Rotatable fixing member, manufacturing method thereof and fixing device

ABSTRACT

A rotatable fixing member includes an elastic layer, a primer layer provided on the elastic layer, and a parting layer provided on the primer layer. The primer layer contains a crystalline fluorocarbon polymer having a functional group and has a thickness of 850 nm or less. The parting layer is a coating layer of a crystalline fluorocarbon polymer.

FIELD OF THE INVENTION AND RELATED ART

The present invention relates to a rotatable fixing member for use in animage forming apparatus such as a copying machine or a printer, amanufacturing method of the rotatable fixing member, and a fixingdevice. Here, the fixing device heats a recording material carryingthereon an image under application of heat and pressure. As such afixing device, it is possible to use a fixing device for fixing ortemporarily fixing an unfixed toner image on the recording material byheating the unfixed toner image, a glossiness (gloss) increasing devicefor increasing glossiness of the image by heating the image fixed on therecording material, a device for drying the recording material, on whichthe image has been formed by an ink jet method, by heating the recordingmaterial, and the like. Further, the rotatable fixing member includes,on a heat-resistant base material, at least an elastic layer, a primerlayer of a fluorocarbon polymer (fluorine-containing resin) and acoating parting layer of a fluorocarbon polymer and can be used as afixing roller, a fixing film, a pressing roller, a conveying roller, andthe like. For the fixing device in the image forming apparatus such asan electrophotographic copying machine or an electrophotographic laserbeam printer, as a method of fixing the unfixed toner image on therecording material under application of heat and pressure, a methodusing the fixing roller or a method using the fixing film is employed.In the fixing roller method, a nip is created by press-contact of aroller (fixing roller) including a heat source as a rotatable heatingmember with a rotatable pressing member (pressing roller) disposed andpaired with the fixing roller. Toner is melted and pressed by passingthe recording material, such as paper on which the unfixed toner imageis carried, through the nip, thus being obtained as a fixed image. Onthe other hand, in the fixing film method, a fixing unit as therotatably heating member in which the heat source is covered with aheat-resistant film (fixing film), and the rotatable pressing member(pressing roller) disposed and paired with the fixing unit create thenip. Through the nip, the recording material carrying thereon theunfixed toner image passes, so that the toner is melted and pressed toobtain the fixed image. The pressing roller used in the fixing devicesof these types requires the elastic layer in order to create a propernip by the press contact and also requires heat resistance so as towithstand use at a toner fixing temperature of 200° C. to 250° C.Further, in order to prevent the toner to depositing on a rollersurface, a parting layer is required to be formed at an outermostsurface. Further, also with respect to the fixing roller or the fixingfilm used in the fixing devices of these types, the parting layer isrequired to be formed at the outermost surface of the fixing roller orthe fixing film since the fixing roller or the fixing film directlycontacts the toner image. Particularly, with respect to the fixingroller or the fixing film for the fixing device for fixing a colorimage, in order to ensure glossiness (gloss) of the fixed image, thereis a need to provide under the parting layer the elastic layer foruniformizing a contact surface with the toner image. Further, both ofthe parting layer and the elastic layer require the heat resistance suchthat the layers can withstand the use at about 200° C. to about 250° C.

As a conventional parting layer, those formed by coating the elasticlayer with a fluorocarbon polymer (fluorine-containing resin) tube, adispersion paint of a fluorocarbon rubber such as a fluorocarbon rubberlatex, and a dispersion paint of a fluorocarbon polymer such aspolytetrafluoroethylene (PTFE) ortetrafluoroethylene-perfluoroalkylvinyl ether copolymer (PFA) have beenused. Further, for the purpose of ensuring good parting property withrespect to the toner, good flatness at the outermost surface is desired.In addition, for the purpose of improving fixability for the fixingroller or the fixing film and for the purpose of reducing a cost of thepredetermined, a layer of the fluorocarbon polymer is desired to be madethin.

The conventional manufacturing method of the parting layer on theelastic layer is roughly classified into two methods. That is, there arecoating method and a method in which the elastic layer is coated with atube of the fluorocarbon polymer. As the coating method in which theparting layer is smoothed and formed in a thin layer, a method asdescribed in Japanese Laid-Open Patent Application (JP-A) 2000-330405 inwhich solvent-soluble non-crystalline fluorocarbon polymer primer layercontaining a cyclic fluorocarbon polymer and a parting layer of anon-crystalline fluorocarbon polymer are used may be used. By using thismethod, it is possible to form the primer layer and the parting layer ina thickness of 25 μm or less in total. However, the non-crystallinefluorocarbon polymer is liable to be softened, so that heat resistivityand durability cannot be sufficiently obtained.

Further, as a generally known coating method, a method as described inJP-A 2003-140491 or JP-A 2006-163315 in which a dispersion paint of acrystalline fluorocarbon polymer primer is used may be employed.However, in the case where this method is employed, the state of theprimer layer is liable to disturb the smoothness of the surface of thefluorocarbon polymer, so that it is very difficult to obtain sufficientsmoothness. In order to obtain the sufficient smoothness, it is requiredthat baking of the parting layer is performed at high temperature for along time and leveling of the fluorocarbon polymer parting layer issufficiently effected, so that the parting layer deteriorates theelastic layer which is an underlying layer of the parting layer.

It has been conventionally very difficult to form on the elastic layerthe fluorocarbon polymer parting layer, which is thin and smooth and hassufficient durability, without deteriorating the elastic layer. Further,in the method using the fluorocarbon polymer tube, from the viewpoint ofhandling during manufacturing, the fluorocarbon polymer tube requiresstrength. For that reason, the tube requires a thickness of about 200 μmand a primer layer formed between the tube and the elastic layerrequires a thickness of about 5 μm, so that a layer having a thicknessof about 25 μm in total is formed. It is difficult in manufacturing tofurther decrease the tube thickness. In addition, the fluorocarbonpolymer tube is harder than the fluorocarbon polymer coating layerhaving the same thickness, thus being less liable to follow therecording material and an uneven toner surface. Further, the tube isgenerally formed by extrusion (molding) but a molecular chain of thefluorocarbon polymer constituting the tube is subjected to a shearingforce to be oriented in an extrusion direction during the extrusion, sothat heat conductivity of the rube with respect to a thickness directionperpendicular to the orientation direction is lowered. For this reason,the constitution of the method using the fluorocarbon polymer tube isnot advantageous in terms of fixability. Thus, it was very difficult toform the fluorocarbon polymer parting layer, which was thin and smoothand had the sufficient durability, on the elastic layer withoutdeteriorating the elastic layer.

SUMMARY OF THE INVENTION

The present invention has been accomplished in view of theabove-described technical problem.

A principal object of the present invention is to provide a rotatablefixing member, prepared by successively laminating at least an elasticlayer, a primer layer and a parting layer on a base material(substrate), capable of compatibly realizing a decrease in thickness ofthe parting layer and surface smoothness of the parting layer whilesuppressing thermal degradation of the elastic layer.

Another object of the present invention is to provide a manufacturingmethod of the rotatable fixing member and to provide a fixing deviceincluding the rotatable fixing member.

According to an aspect of the present invention, there is provided arotatable fixing member comprising:

an elastic layer;

a primer layer provided on the elastic layer; and

a parting layer provided on the primer layer,

wherein the primer layer contains a crystalline fluorocarbon polymerhaving a functional group and has a thickness of 850 nm or less, and

wherein the parting layer is a coating layer of a crystallinefluorocarbon polymer.

According to another aspect of the present invention, there is provideda fixing device comprising:

a rotatable fixing member including an elastic layer, a primer layerprovided on the elastic layer, and a parting layer provided on theprimer layer; and

a back-up member for creating a fixing nip together with the rotatablefixing member,

wherein the primer layer contains a crystalline fluorocarbon polymerhaving a functional group and has a thickness of 850 nm or less, and

wherein the parting layer is a coating layer of a crystallinefluorocarbon polymer.

According to a further aspect of the present invention, there isprovided a manufacturing method of a rotatable fixing member includingan elastic layer, a primer layer and a parting layer, the manufacturingmethod comprising:

a first step of applying a dispersion containing a crystallinefluorocarbon polymer having a functional group onto a surface of anelastic layer;

a second step of forming a primer layer by drying the dispersion;

a third step of decreasing a thickness of the primer layer to 850 nm orless by removing a part of the primer layer on a surface side of theparting layer; and

a fourth step of forming a parting layer by coating a crystallinefluorocarbon polymer onto the surface of the primer layer decreased inthickness and then by baking the coated crystalline fluorocarbonpolymer.

These and other objects, features and advantages of the presentinvention will become more apparent upon a consideration of thefollowing description of the preferred embodiments of the presentinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic structural view of an example of an image formingapparatus, and FIG. 1B is a schematic cross-sectional view of a fixingdevice in Embodiment 1.

FIG. 2( a) is a schematic sectional view showing a layer structure of afixing film which is a rotatable fixing member, and FIG. 2( b) is aschematic view of a rising coating machine.

FIG. 3( a) is a scanning electron microscope (SEM) photograph showing astate of a primer layer in Embodiment 1, FIG. 3( b) is an SEM photographshowing a state, in which coating grains are fixed and laminated withoutbeing subjected to leveling, of the primer layer formed by dry coatingin Comparative Embodiment 1, and FIG. 3( c) is an SEM photograph showingthe state of the primer layer formed by dry coating in ComparativeEmbodiment 1 and is also an enlarged photograph of fixed grains shown inFIG. 3( b) with the same magnification as that in FIG. 3( a).

FIG. 4( a) is a schematic view showing a state of a primer layer formedby wet coating in Comparative Embodiment 4, FIG. 4( b) is a schematicview showing a state in which a parting layer is applied onto the primerlayer formed by wet coating and then is dried, and FIG. 4( c) is aschematic view showing a state in which the parting layer is appliedonto the primer layer formed by wet coating and then dried and baked.

FIG. 5( a) is a schematic view showing a state of a primer layer formedby dry coating in Comparative Embodiment 1, and FIG. 5( b) is aschematic view showing a state in which a parting layer is applied ontothe primer layer formed by dry coating and then is dried in ComparativeEmbodiment 1.

FIG. 6( a) is a schematic view showing a primer layer in Embodiment 1,and FIG. 6( b) is a schematic view showing a state in which a partinglayer is applied onto the primer layer and then is dried in Embodiment1.

FIG. 7( a) is a schematic cross-sectional structural view of a fixingdevice in Embodiment 2, and FIG. 7( b) is a schematic sectional view ofa fixing roller which is a rotatable fixing member in Embodiment 2.

FIG. 8( a) is a graph showing a relationship between a primer layerthickness and a gloss value (glossiness) with respect to fixing rollershaving a parting layer thickness of 15 μm in Embodiment 2 andComparative Embodiments, and FIG. 8( b) is a graph showing arelationship between the primer layer thickness and the glossiness withrespect to fixing rollers having a parting layer thickness of 8 μm inEmbodiment 2 and Comparative Embodiments.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 (1) Image FormingApparatus

FIG. 1A is a schematic structural view showing an example of an imageforming apparatus 10 in which a fixing device 114 according to thepresent invention is mounted as a fixing device for fixing an unfixedtoner image on a recording material by heating the unfixed toner image.This image forming apparatus 100 is a color printer of anelectrophotographic type. The image forming apparatus 100 effects colorimage formation on a sheet-like recording material P as a recordingmedium on the basis of an electrical image signal input from an externalhost device 200 such as a personal computer or an image reader into acontrol circuit portion (control portion) 101 of the image formingapparatus 100. The control circuit portion 101 includes a CPU (computingportion) and an ROM (storing means) and transfers various pieces ofelectrical information between itself and the host device 200 or anoperating portion (not shown) of the image forming apparatus 100.Further, the control circuit portion 101 effect centralized control ofan image forming operation of the image forming apparatus 100 inaccordance with a predetermined control program or a predeterminedreference table.

Four image forming portions Y, C, M and K for forming color toner imagesof yellow (Y), cyan (C), magenta (M) and black (K) are successivelydisposed from a lower portion to an upper portion in this order in theimage forming apparatus 100. Each of the image forming portions Y, C, Mand K includes an electrophotographic photosensitive drum 51 as an imagebearing member, and a charging device 52, a developing device 53, acleaning device 54, and the like which are process means acting on thedrum 51. A yellow toner as a developer is accommodated in the developingdevice 53 of the image forming portion Y. A cyan toner as the developeris accommodated in the developing device of the cyan image formingportion C. A magenta toner as the developer is accommodated in thedeveloping device of the magenta image forming portion M. A black toneras the developer is accommodated in the developing device of the blackimage forming portion K. An optical system 55 for forming anelectrostatic image by exposing the drum 51 to light is providedcorrespondingly to the four color image forming portions Y, C, M and K.As the optical system 55, a laser scanning exposure optical system isused. In each of the image forming portions Y, C, M and K, the drum 51which has been uniformly charged by the charging device 52 is subjectedto scanning exposure on the basis of image data by the optical system55. As a result, the electrostatic latent image corresponding to ascanning exposure image pattern is formed on the drum surface. Theelectrostatic latent image is developed into a toner image by thedeveloping device 53. That is, on the drum 51 of the yellow imageforming portion Y, a yellow toner image corresponding to a yellowcomponent image of a full-color image is formed. On the drum 51 of thecyan image forming portion C, a cyan toner image corresponding to a cyancomponent image of the full-color image is formed. On the drum 51 of themagenta image forming portion M, a magenta toner image corresponding toa magenta component image of the full-color image is formed. On the drum51 of the black image forming portion K, a black toner imagecorresponding to a black component image of the full-color image isformed.

The color images formed on the drums 51 of the image forming portions Y,C, M and K are successively superposed and primary-transferred, in apredetermined aligned state, onto an intermediary transfer member 56which is rotated at the substantially same speed as that of the drums 51in synchronism with rotations of the drums 51. As a result, an unfixedfull-color toner image is synthetically formed on the intermediarytransfer member 56. In this embodiment, as the intermediary transfermember 56, an endless intermediary transfer belt is used and is woundaround and stretched by three rollers of a driving roller 57, asecondary transfer opposite roller 58 and a tension roller 59, and isdriven by the driving roller 57. As a primary transfer means forprimary-transferring the toner image from each of the drums 51 of theimage forming portions Y, C, M and K, a primary transfer roller 60 isused. To the roller 60, a primary transfer bias of an opposite polarityto a charge polarity of the toner is applied from an unshown biasvoltage source. As a result, the toner image is primary-transferred fromeach of the drums 51 of the image forming portions Y, C, M and K ontothe belt 56.

After the primary transfer of the toner image from each of the drum 51of the image forming portions Y, C, M and K onto the belt 56, tonerremaining on each of the drums 51 as residual toner is removed by thecleaning device 54. The steps described above are performed insynchronism with the rotation of the belt 56 with respect to each ofyellow, cyan, magenta and black, so that the primary-transfer tonerimages of the respective colors are successively formed superposedly onthe belt 56. Incidentally, during image formation on only a single color(single color mode), the above-described steps are performed withrespect to only an objective color. On the other hand, the recordingmaterial P in a recording material cassette 61 is separated and fed oneby one by a feeding roller 62 with predetermined timing. Then, therecording material P is conveyed to a transfer nip, which is apress-contact portion between a secondary transfer roller 64 and anintermediary transfer belt portion wound about the secondary transferopposite roller 58, by registration rollers 63 with predeterminedtiming.

The synthetic primary transfer toner images formed on the belt 56 arecollectively transferred onto the recording material P by a bias, of anopposite polarity to the toner charge polarity, applied from an unshownbias voltage source. Secondary transfer residual toner remaining on thebelt 56 after the secondary transfer is removed by an intermediarytransfer belt cleaning device 65. The unfixed toner imagesecondary-transferred onto the recording material P is melt-mixed andfixed on the recording material P by a fixing device 114, and is sent toa sheet discharge tray 67 through a sheet discharging path 66 as afull-color print.

(2) Fixing Device 114

FIG. 1B is a schematic cross-sectional view of a principal part of thefixing device 114 in this embodiment (Embodiment 1). Here, with respectto the fixing device and members constituting the fixing device, alongitudinal direction is a direction perpendicular to a recordingmaterial conveyance direction in a plane of the recording material. Awidthwise direction is a direction parallel to the recording materialconveyance direction in the plane of the recording material. A width isa dimension with respect to the widthwise direction. A length is adimension with respect to the longitudinal direction. The fixing device114 in this embodiment is basically of the film heating type which is aso-called known tension-less type. The fixing device 114 of this filmheating type uses a heat-resistant fixing film 2, which has flexibilityand has an endless belt shape or a cylindrical shape, as the rotatablefixing member. At least a part of a circumferential portion of thefixing film 2 is always in a tension-free state (in which no tension isapplied), and the fixing film 2 is rotationally driven by a rotationdriving force of the rotatable pressing member (pressing member) 6.

The fixing film 2 is, as described later, prepared by successivelylaminating at least the elastic layer, the primer layer and the partinglayer on the base material. The primer layer contains a crystallinefluorocarbon polymer having a functional group and has a thickness of850 nm or less. The parting layer is a coating layer of a crystallinefluorocarbon polymer. The fixing film 2 is a film including the partinglayer which is an outermost surface layer and is formed in a smallthickness and smoothed, and enables improvement in fixability of thefixing device 114 and output of a high-gloss image.

Inside the film 2, a stay 1 as a heating member supporting member and afilm guide member is provided. The stay 1 is a rigid member of aheat-resistant resin material which is elongated in the longitudinaldirection (perpendicular to the drawing) and has a substantiallysemicircular trough cross section. In this embodiment, as a material forthe stay 1, a heat-resistant liquid crystal polymer is used. In theneighborhood of a longitudinal central portion of the stay 1, a hole 1 bin which a thermistor (temperature detecting element) 5 to be disposedto contact a heater 3 is accommodated is provided in communication witha groove portion 1 a. The heater 3 is a so-called ceramic heater in thisembodiment and is engaged in and fixedly supported by the groove portion1 a provided at a widthwise central portion on a lower surface of thestay 1 along the longitudinal direction of the stay 1.

The heat-resistant cylindrical fixing film 2, as the rotatable fixingmember, which has flexibility and is excellent in heat resistivity isloosely engaged externally on an outer circumferential surface of thestay 1, which supports the heater 3, with a circumferential margin.Further, onto an inner circumferential surface of the film 2, grease isapplied in order to improve slidability with respect to the heater 3.The stay 1, the heater 3, the film 2 and the like constitute a heatingassembly 4. An elastic pressing roller (rotatable pressing member) 6 asa back-up member in this embodiment is prepared by coating a siliconefoam member as a heat-resistant elastic layer 6 b on a cylindrical shaftcore metal 6 a of iron, stainless steel, aluminum, or the like and thenby coating a fluorocarbon polymer tube as a parting layer 6 c on theelastic layer 6 b. The roller 6 opposes the heater 3 held by the stay 1through the film 2. Further, a predetermined pressure is exerted betweenthe stay 1 and the roller 6 by a pressing mechanism (not shown). By thispressure, the elastic layer 6 b of the roller 6 is elastically deformedwith respect to the longitudinal direction along the heater 3 throughthe film 2. As a result, a nip (fixing nip) N having a predeterminedwidth necessary to heat-fix an unfixed toner image T carried by therecording material P is created between the roller 6 and the film 2pressed against the heater 3.

The roller 6 is rotationally driven in a counterclockwise directionindicated by an arrow at a predetermined speed by a motor (drivingmeans) M controlled by the control circuit portion 101 at least duringexecution of the image formation. By a frictional force created in thenip N between the roller 6 and the film 2 by the rotation of the roller6, a rotational force acts on the film 2. As a result, the film 2 isrotated around the stay 1 in a clockwise direction indicated by an arrowat a peripheral speed substantially corresponding to the rotationalperipheral speed of the roller 6 while intimately sliding on the surfaceof the heater 3 in the nip N at the inner surface of the film 2. Thatis, the film 2 is rotated at the peripheral speed substantially equal tothe conveyance speed of the recording material P, carrying thereon theunfixed toner image T, which is conveyed from an image transfer portionside. Further, the heater 3 is increased in temperature by beingsupplied with electric power from a power supply 102. The temperature ofthe heater 3 is detected by the thermistor 5. Detected temperatureinformation is fed back to the control circuit portion 101. The controlcircuit portion 101 controls the electric power input from the powersupply 102 to the heater 3 so that a detected temperature input from thethermistor 5 is kept at a predetermined target temperature (fixingtemperature).

In a state in which the heater 3 is heated and temperature-controlled atthe predetermined fixing temperature and the roller 6 is rotationallydriven, the recording material P carrying thereon the unfixed tonerimage T is introduced into the nip N with a toner image carrying surfacetoward the film 2 side. The recording material P intimately contacts theouter surface of the film 2 in the nip N and is nip-conveyed in the nipN together with the film 2. As a result, heat of the heater 3 is appliedto the recording material P through the film 2 and the pressing force isapplied to the recording material P in the nip N, so that the unfixedtoner image T is thermally press-fixed on the surface of the recordingmaterial P. The recording material P which has passed through the nip Nis self-separated from the outer circumferential surface of the film 2and is conveyed to the outside of the fixing device 114.

(3) Fixing Film 2

FIG. 2( a) is a schematic sectional view showing a layer structure ofthe fixing film 2 which is the rotatable fixing member in the fixingdevice 114 described above. The fixing film 2 includes a base material2A which is a cylindrical metal member or an endless belt member of aheat-resistant resin material. The film 2 may preferably have a smalltotal thickness in order to improve a quick start property by decreasingthermal capacitor, and therefore a smaller thickness of the basematerial 2A is more advantageous in terms of the quick start of thefixing device 114. However, when the thickness of the base material 2Ais excessively small, the thickness of the base material 2A maypreferably be 20-100 μm. On the outer circumferential surface of thebase material 2A, an elastic layer 2B is formed. The elastic layer 2Bhas the function of transferring the heat from the heater 3 to therecording material P or the toner T so as to cover the base material 2Awhile following unevenness of the recording material P or the toner T.As a material for the elastic layer 2B, it is possible to use aheat-resistant rubber in which a high heat-conductive filler is mixed.With respect to the thickness of the elastic layer 2B, a thinner elasticlayer 2B is more advantageous in terms of the quick start of the fixingdevice 114. However, when the elastic layer 2B is excessively thin, aneffect of covering the recording material P or the toner T is weaken, sothat the thickness of the elastic layer 2B may preferably be in therange from 50 μm to 1 mm, more preferably be 80 μm or more and 300 μm orless. A parting layer 2C which is the outermost surface layer of thefilm 2 is formed of a fluorocarbon polymer (fluorine-containing resin)having a good parting property such that the toner T on the recordingmaterial P causes offset. Further, between the elastic layer 2B and theparting layer 2C, a primer layer 2D for ensuring adhesiveness betweenthe elastic layer 2B and the parting layer 2C is provided. In order toeasily conduct the heat from the heater 3 to the recording material Pand the toner T, a total thickness of the parting layer 2C and theprimer layer 2D may desirably be 25 μm or less.

(3-1) Base Material 2A

As the base material 2A, in addition to metal such as SUS (steel usestainless), nickel or nickel alloy, a thermosetting resin materialhaving heat resistivity, strength, durability and the like, such aspolyimide or polyamideimide can be used.

(3-2) Elastic Layer 2B

As a material for the elastic layer 2B, e.g., a heat-resistant rubbersuch as a silicone rubber or a fluorocarbon rubber is used.Particularly, of the silicone rubber, an addition curing silicone rubberis frequently used from the viewpoint of a processing property. That is,the material of the elastic layer 2B is the silicone rubber or thefluorocarbon rubber.

(3-2-1) Addition Curing Silicone Rubber

In general, the addition curing silicone rubber includesorganopolysiloxane having an unsaturated aliphatic group,organopolysiloxane having active hydrogen bound to silicon, and aplatinum compound as a cross-linking catalyst.

An example of organopolysiloxane having an unsaturated aliphatic groupincludes the following.

a) Straight-chain organopolysiloxane wherein both molecule terminals areexpressed by R¹ ₂R²SiO_(1/2), and an intermediate unit is expressed byR¹ ₂SiO and R¹R²SiO.

b) Branched polyorganosiloxane wherein R¹SiO_(3/2) to SiO_(4/2) areincluded in the intermediate unit.

Here, R¹ represents a monovalent non-substituted or substitutedhydrocarbon group which does not include the aliphatic unsaturated groupbonded to a silicon atom. Specifically, the following is included:

c) an alkyl group (for example, methyl, ethyl, propyl, butyl, pentyl,hexyl, and the like);

d) an aryl group (phenyl group); and

e) a substituted hydrocarbon group (for example, chloromethyl,3-chloropropyl, 3,3,3-trifluoropropyl, 3-cyanopropyl, 3-methoxypropyl,and the like).

Particularly, since synthesis and handling are easy and excellent heatresistance can be obtained, 50% or more of R¹ is preferably a methylgroup, and all R¹ are particularly preferable to be the methyl group.

Further, R² represents the unsaturated aliphatic group bonded to asilicon atom, and a vinyl, allyl, 3-butenyl, 4-pentenyl, 5-hexynyl areillustrated, and since synthesis and handling are easy, and across-linking reaction can be easily performed, vinyl is preferable.

Further, organopolysiloxane having the active hydrogen bonded to siliconis a cross-linking agent, which forms a cross-linked structure by thereaction with an alkenyl group of an organopolysiloxane component havingthe unsaturated aliphatic group by a catalytic action of the platinumcompound.

The number of hydrogen atoms bonded to the silicon atom is a numberexceeding three pieces in average in one molecule.

As an organic group bonded to the silicon atom, a non-substituted orsubstituted monovalent hydrocarbon group can be illustrated, which is inthe same range as R¹ of the organopolysiloxane component having theunsaturated aliphatic group. Particularly, since synthesis and handlingare easy, a methyl group is preferable.

A monocular weight of organopolysiloxane having active hydrogen bondedto silicon is not particularly limited.

Further, viscosity of organopolysiloxane at 25° C. is preferably in therange of 10 mm²/s or more and 100,000 mm²/s or less, and more preferably15 mm²/s or more and 1,000 mm²/s or less. The reason why viscosity ofthe organopolysiloxane at 25° C. is preferably in the above describedrange is because it does not happen that a desired cross-linkingproperties and physical properties of molded articles are not obtaineddue to evaporation during preservation, and moreover, synthesis andhandling are easy so that it can be easily diffused in the system.

A siloxane base can be in the shape of any of a straight-chain, branchedor circular, and a mixture of these shapes may be used. Particularly,because of easiness of synthesis, the shape of a straight-chain ispreferable. A Si—H binding may be present in whichever siloxane unit inthe molecule, but at least a part thereof is preferably present in asiloxane unit of the molecule terminal such as an R¹ ₂HSiO_(1/2) unit

As the addition curing silicone rubber, an amount of the unsaturatedaliphatic group is preferably 0.1 mol % or more and 2.0 mol % or lessfor silicon atom 1 mol, and particularly, more preferably 0.2 mol % ormore and 1.0 mol % or less.

Further, the unsaturated aliphatic groups and active hydrogens areblended in such a ratio that ratio of the number of active hydrogens tounsaturated aliphatic groups is preferably 0.3 or more and 0.8 or less.The ratio of the number of active hydrogens to unsaturated aliphaticgroups can be quantitatively calculated by measurement using HydrogenNuclear Magnetic Resonance Analysis (for example, ¹H-NMR (Model Name:AL400 type FT-NMR made by Nihon Denshi Kabushiki Kaisha). By setting theratio of the number of active hydrogens to unsaturated aliphatic groupswithin the above described numerical range, the hardness of the siliconerubber layer after curing can be stabilized. Further, an excessive riseof the hardness can be suppressed.

(3-2-2) Filler in Elastic Layer 2B and Thermal Conductivity of ElasticLayer 2B

As the high heat-conductive filler to be mixed in the rubber material ofthe elastic layer 2B, it is possible to use alumina, aluminum nitride,boron nitride, carbon, carbon nanofiber, metal silicon, zinc oxide,silicon oxide, etc. These materials can be used singly or in mixture oftwo or more species. In order to obtain a sufficient fixability, a highheat-conductive rubber having the thermal conductivity of 0.7 W/m·k ormore and 2.0 W/m·k or less may desirably be used.

(3-3) Primer Layer 2D

Between the elastic layer 2B and the parting layer 2C, the primer layer2D for bonding the elastic layer 2B of the silicone rubber and theparting layer of the fluorocarbon polymer is provided. A material forthe primer layer 2D is a dispersion containing a crystallinefluorocarbon polymer having a functional group and containing water. Thedispersion may preferably contain a crystalline fluorocarbon polymerhaving no functional group in addition to the crystalline fluorocarbonpolymer having the functional group. Examples of the functionalgroup-containing crystalline fluorocarbon polymer are described in JP-A(Tokuhyo) 2002-514181, Japanese Patent No. 2882579 and JP-A 2005-212318.The functional group contributes to the bonding of the parting layer tothe elastic layer.

Examples of the functional group may include ester, alcohol, acid, theirsalts, their halides, cyanate, carbamate, nitrile, etc. Examples of acidmay include carbon-based acid, sulfur-based acid, phosphorus-based acid.The functional group-containing fluorocarbon polymer can, e.g., beobtained by copolymerizing a fluorinated monomer having a pendant-typeside group containing a functional group unit when the fluorocarbonpolymer is manufactured by polymerization. A preferred example of such afunctional group may include the phosphorus-based acid, particularly aphosphate group. A preferred example of the fluorinated monomer havingthe phosphate group as the functional group may include an esterdihydrogenphosphate compound having a trifluoro-vinyl-ether group. Aspecific example thereof may include dihydrogenphosphate2,2,3,3,5,6,6,8,9,9-decafluoro-5-trifluoromethyl-4,7-dioxanona-8-ene-1-yl (EVE-P) and dihydrogenphosphate2,2,3,3,4,4,6,7,7-nonafluoro-5-oxahepta-6-ene-1-yl.

The fluorocarbon polymer is a copolymer which can be obtained bycopolymerizing tetrafluoroethylene (TFE) with at least one species of afluorine substitution comonomer by a known method. Examples of thefluorine substitution comonomer may include perfluoroalkylvinylcompounds having 3-8 carbon atoms, and perfluoroalkylvinylethers (PFAV)in which alkyl group has 1-5 carbon atoms. A copolymer resin (PFA resin)between TFE and perfluoroalkyl-vinylether or a copolymer resin betweenTFE and perfluoroalkylvinyl compound is a preferred fluorocarbonpolymer. The functional group-containing fluorocarbon polymer isobtained by copolymerizing the above-mentioned fluorinated monomercontaining the functional group unit when the fluorocarbon polymer ismanufactured by the polymerization. In a most preferable examplefluorocarbon polymer is the copolymer resin (PFA resin) between TFEhaving a side chain containing the phosphate group andperfluoroalkylether. A melting point of the functional group-containingfluorocarbon polymer is 200-300° C., preferably 220-280° C. For thatreason, proportion of the alkylvinylether component or the alkylvinylcomponent to the copolymer resin is in the range of 3-15 mol. %,preferably 5-12 mol. %.

The fluorocarbon polymer having no functional group can be used by beingappropriately selected from the fluorocarbon polymers described above.Of the fluorocarbon polymers, the TFE/perfluoroalkylvinylether copolymerresin or the TFE/perfluoroalkylvinyl copolymer resin is preferably used.The copolymer in which the proportion of the alkylvinylether componentor the alkylvinyl component to the copolymer resin is 3-15 mol. %,preferably 5-12 mol. % is preferable from the viewpoint of a desirablemelting point.

In the mixture between the functional group-containing fluorocarbonpolymer and the fluorocarbon polymer containing no functional group, thecontent of the functional group can be adjusted easily and arbitrarily.The functional group-containing fluorocarbon polymer is mixed in anamount of 100-10 wt. %, preferably 80-30 wt. % per the mixture. Themixing of the functional group-containing fluorocarbon polymer with thefluorocarbon polymer containing no functional group can be performed bya known method. The melting point of the mixture may be 200-300° C.,preferable 220-280° C. in consideration of baking temperature such thatthe base material is not damaged by heat when the coating of thefluorocarbon polymer is formed on the base material. Therefore, thecopolymer in which the proportion of the alkylvinylether component orthe alkylvinyl component to the mixture (copolymer resin) is 3-15 mol.%, preferably 5-12 mol. % may preferably be used from the viewpoint thatthe copolymer resin has the desirable melting point. The amount of thefunctional group in the mixture is 0.02-5 mol. %, preferably 0.1-2.5mol. % per the mixture. The primer layer is formed by using an aqueousdispersion in which the mixture is dispersed as fine particles in anaqueous (water) solvent.

(3-4) Parting Layer 2C

The fluorocarbon polymer for the parting layer 2C is insoluble insolvent since the fluorocarbon polymer is consisting of a fluorocarbonpolymer mixture containing the crystalline fluorocarbon polymer. Forthat reason, the fluorocarbon polymer is used in the form of thedispersion in which the fine particles (primary particle size of 830 nmor less) of the fluorocarbon polymer are dispersed in the solvent suchas water. Incidentally, herein, the value of the primary particle sizerefers to a measured value by a scanning electron microscope (SEM). Thecrystalline fluorocarbon polymer has high heat resistivity and highdurability and generally has the melting point of 200° C. or more but inthe case where the crystalline fluorocarbon polymer is used for therotatable fixing member, the rotatable fixing member may preferablywithstand continuous use at 200° C. or more. Generally, the polymercauses partial melting even at the melting point or less and aresin-melting temperature range including the melting point as a centervalue is present and therefore the melting point may preferably be 250°C. or more for the purpose that the rotatable fixing member withstandscontinuous use.

Specific examples of the fluorocarbon polymer may include PFA, FEP(tetrafluoroethylene-hexafluoropropylene copolymer), copolymers thereof,and their modified resins. Particularly, PFA has the melting point of280-320° C. and has a very good heat resistivity and a good processingproperty, thus being a suitable material as the fluorocarbon polymerused in the present invention. Generally, the fluorocarbon polymerhaving a higher melting point was excellent in heat resistivity anddurability but was not melted readily, so that it was difficult to forma film. However, according to the manufacturing method of the presentinvention, it is possible to obtain a good film-forming property even inthe case where the fluorocarbon polymer is PFA such that the meltingpoint is relatively high, i.e., 300° C. or more at which it has beenconventionally difficult to form a film.

(4) Manufacturing Method of Fixing Film 2 (4-1) Formation of ElasticLayer 2B

On the surface of the base material 2A which has been treated with aprimer in advance, the elastic layer 2B is formed. As a method offorming the elastic layer 2B, a ring coating method can be used. FIG. 2(b) shows an example of a ring coating device used in a step of formingthe silicone rubber layer constituting the elastic layer 2B on the basematerial 2A and is a schematic view for illustrating the so-called ringcoating method. The base material 2A which is an endless belt member isput on a cylindrical core 18 which has a perfect circle in cross sectionand the circumference of the circle is substantially equal to an innercircumferential length of the base material 2A, and is mounted on thecore 18. Next, the core 18 on which the base material 18 is mounted isfixed on a movable stage 34 by a chucking attachment 35. A highheat-conductive addition curing silicone rubber composition containingthe addition curing silicone rubber and the high heat-conductive filleris filled in a cylinder pump 32. Then, the composition is pressure-fedby a pressure-feeding motor M1, so that the composition is applied froman application liquid supplying nozzle 33 onto the circumferentialsurface of base material 2A. At this time, simultaneously with theapplication, the movable stage 34 on which the base material 2A and thecore 18 are fixed is moved in a rigid direction in FIG. 2( b) at aconstant speed by a driving motor M2. As a result, the coating film ofthe addition curing silicone rubber composition G constituting theelastic layer 2B can be formed on the entire outer circumferentialsurface of the base material 2A. The thickness of the coating filmconstituting the elastic layer 2B can be controlled by a clearancebetween the application liquid supplying nozzle 33 and the base material2A, a feeding speed of the silicone rubber composition, a movement speedof the base material 2A (stage 34), and the like. The addition curingsilicone rubber layer formed on the base material 2A is heated for acertain time by a known heating means such as an electric furnace or aninfrared heater to promote cross-linking reaction, thus being formedinto the elastic layer 2B which is a cured silicone rubber layer. Themethod of forming the elastic layer 2B is not limited to the ringcoating method described above. For example, it is also possible to usea method in which the material such as a liquid silicone rubber iscoated in a uniform thickness on the metal layer by a means (method)such as a blade coating method and then is heat-cured. It is alsopossible to use a method in which the material such as the liquidsilicone rubber is injected into a mold and then is heat-cured, a methodof heat-curing the material after extrusion molding, a method ofheat-curing after ejection molding, and the like.

The surface of the elastic layer 2B may desirably be subjected tosurface treatment before the primer layer 2D is formed. For example, itis desirable that hydrophilizing treatment is performed through UVtreatment (UV irradiation treatment). This UV treatment is not essentialbut the silicone rubber surface is hydrophilized by the UV treatment anda tacking property is lowered, so that formation of the primer layer 2Din a very small thickness and formation of the parting layer 2C when aresubsequently effected become easy.

(4-3) Formation of Primer Layer 2D

In order to obtain good surface smoothness of the parting layer 2C, theprimer layer 2D on the elastic layer 2B is required to be formed in athickness of 830 nm or less, preferably 360 nm or less so as to coverthe entire area of the elastic layer 2B. For that purpose, the method offorming the primer layer 2D on the elastic layer 2B may desirablyinclude at least three steps (First to third steps) described below. Thefirst step is a step of applying the dispersion of the primer so as tocover the entire area of the elastic layer. Then, in the second step,the coating layer of the primer layer is dried to obtain a dried primerlayer. Then, in the third step, a part of the dried primer layer isremoved to decrease and uniformize the layer thickness. Thus, it isdesirable that the primer layer is formed by the three steps describedabove. This is because it is generally very difficult to apply thefluorocarbon polymer dispersion onto the elastic layer 2B in a thicknessof 830 nm or less in a single step of the known method. Generally, whenthe primary particle size is about 1 μm with respect to fine particles,Van der Waals force acting among the fine particles is not negligible.The fine particles are liable to agglomerate and are more liable toagglomerate with a smaller particle size. Particularly, theagglomeration is liable to occur when the particles are being dried. Forthat reason, in the case where the dispersion is only applied in a smallthickness by the known method, the primary particles agglomeratetogether and are dried in a state in which the primary particles formaggregate or layer of several μm or more in primary particle size. Forthat reason, only applying and drying the primer through the generalmethod, it is substantially impossible to form a uniform layer havingthe thickness of 830 nm or less. Therefore, the coating (application)layer of the dispersion is first formed in advance in the first step andthe dried primer layer is formed in the second step, and then in thethird step, the part of the dried primer layer is removed to adjustlayer thickness to 830 nm or less. In a final fourth step, the primerlayer decreased in thickness is coated with the crystalline fluorocarbonpolymer, followed by baking to obtain the parting layer.

In the firsts step, the application of the fluorocarbonpolymer-dispersed aqueous paint, which is the primer, onto the elasticlayer may be performed by a known method such as spraying or dipping.The drying in the second step may be performed by drying through naturaldrying or air blowing, so that the dried primer layer can be formed. Inthe dried primer layer, mud cracks may preferably be created byadjusting a solid content of the fluorocarbon polymer in thefluorocarbon polymer-dispersed aqueous point as the primer, and anapplication amount and a drying method of the paint, and the like. Withrespect to the mud-cracked dried primer layer, the subsequent third stepcan be performed very easily. The cracks are liable to occur with anincreasing thickness but when the paint is applied in an excessive largethickness, dropping occurs and utilization factor is poor. Therefore,the thickness of the primer layer may desirably be about 4 μm to about 7μm.

The removal in the third step can be performed by using a method inwhich an abutting member (scraping member) such as cloth, paper orsponge against the dried primer layer to scrape the surface of the driedprimer layer off the dried primer layer. Further, it is possible to usea method in which the surface of the dried primer layer is blown offwith high-pressure air or gas (by blowing the air or gas onto the driedprimer layer). It is also possible to use a method in which the surfaceof the dried primer layer is washed with a liquid such as water or otherliquids, and the like method. The primer particles present immediatelyon the elastic layer at a lowermost layer portion physically andchemically bond to the elastic layer with a force stronger than anadhesion force among the primer particles, thus being less dropped(removed) compared with the primer particles present above those presentimmediately on the lowermost layer portion.

Generally, the surface of the silicone rubber has strong waterrepellency due to its chemical structure. When the water repellency isstrong, the primer dispersion is repelled by the silicone rubbersurface, so that the primer dispersion is not readily applied onto theentire surface of the elastic layer. In addition to the waterrepellency, the elastic layer possesses the tacking property. When thetacking property is excessively strong, friction between a nonwovenfabric (“BEMCOT”, mfd. by Asahi Kasei Fibers Corp.) which is theabutting member and the roller becomes excessively strong, so that theabutting member is liable to vibrate and therefore the uniform removalin the removing step described above is less liable to be effected. Forthis reason, in order to lower the surface water repellency and thetacking property, it is desirable that the surface of the elastic layer2B is subjected to the UV treatment. The degree of the UV treatment maydesirably be such that the lowering in water repellency is at a levelthat it can be recognized. As an index thereof, the surface of theelastic layer 2B may be UV-treated so that a contact angle with purewater is 90 degrees or less as measured by a contact angle meter(“FACE”, mfd. by Kyowa Interface Science Co., Ltd.). As a result,crawling during the dispersion application and vibration in the removingstep do not readily occur, so that the primer layer which is a thinlayer can be uniformly formed on the surface of the elastic layer 2Beasily. However, even in the case where there is the tacking property,by repeating the abutting step of the nonwoven fabric (BEMCOT), it ispossible to finally obtain the uniform thin primer layer 2D. Generally,the wavelength of visible light is about 360 nm to obtain 830 nm andwhen a surface unevenness (roughness) is smaller than the visible lightwavelength, diffused reflection of visible light is suppressed andtherefore a surface gloss becomes very good.

When the surface unevenness is extended on the primer layer 2D, thesurface smoothness of the parting layer 2C is largely impaired by theinfluence of the surface unevenness. However, when at least thethickness of the primer layer 2D is 830 nm or less, a degree of thesurface unevenness of the primer layer 2D is not more than the visiblelight wavelength. That is, the thickness of the primer layer obtained bythe forming step described above may preferably be not more than a lowerlimit of the visible light wavelength. As a result, the diffusedreflection of visible light is prevented, so that gloss feeling becomesgood. Particularly, when the thickness of the primer layer 2D is notmore than 360 nm which is the lower limit of the visible lightwavelength, the unevenness of not less than the visible light wavelengthcannot be present. Thus, the diffused reflection does not occur in theentire wavelength region of visible light.

The primer layer 2D is constituted by the fine particles of thefluorocarbon polymer mixture containing the crystalline fluorocarbonpolymer as the primer. For that reason, the primary particle size of thefine particles of the fluorocarbon polymer mixture is required at leastto be 830 nm or less. In order to obtain a particularly good glosssurface, it is desirable that the fine particles having the primaryparticle size of 360 nm or less are used. Particularly, when the primaryparticle size of the fluorocarbon polymer primer is 360 nm or less, thefine particles are not scraped off even when the cloth abutting memberis abutted against the primer layer, so that the primer particles at thelowermost portion (contacting the elastic layer 2B) are further liableto remain. That is, the dispersion of the fluorocarbon polymer mixtureto be applied onto the surface of the elastic layer 2B in order to formthe dried primer layer may preferably contain the fluorocarbon polymerfine particles having the primary particle size of 360 nm or less. Byadjusting an abutting force or the like of the abutting member, it ispossible to create a state as shown in FIG. 3( a) in which only asingle-particle layer of the fluorocarbon polymer primer primaryparticles present at the lowermost portion (contacting the elastic layer2B) of the primer layer 2D is left. FIG. 3( a) is an SEM (scanningelectron microscope) photograph showing the state of the primer layer 2Din which only the single-particle layer is left. The thickness of theprimer layer 2D is not always required to be 850 nm or less in theentire area. Even when a portion of 1 μm or more and several μm or lessis locally present, such thickness may be permitted if the portion isinconspicuous when the portion is covered with the parting layer 2C.Further, the primer particle layer may also be locally omitted and 70%or more of an area of the primer layer surface may only be required tobe formed on the smooth surface of 850 nm or less in thickness. When thearea in which the primer particles are not placed on the elastic layer2B is less than 30%, it is possible to obtain a good bonding propertytogether with good gloss. When the thin primer layer having thethickness of not more than the visible light wavelength is formed on theelastic layer 2B<structural color can appear on the elastic layersurface by optical (light) interference phenomenon. This phenomenon ofappearance of the structural color is generally a phenomenon thatvisible light causes interference to produce the structural color basedon a minute structure of not more than the visible light wavelength, sothat the presence of the primer layer of the fluorocarbon polymer primerfine particles of the visible light wavelength on the elastic layer canbe confirmed by checking the presence or absence of the appearance ofthe structural color. Particularly, when the primer layer 2D is formedin the single-particle layer of the primary particles of the primer, itis possible to produce a desired structural color by adjusting theprimary particle size. That is, reflected light at the surface of theprimer layer 2D and reflected light at the surface of the elastic layer2B which is below the surface of the primer layer 2D by a thicknesscorresponding to the primary particle size interfere with each other, sothat the structural color appears. Therefore, it is possible to producea desired structural color by adjusting the thickness, i.e., the primaryparticle size. For that reason, also in the manufacturing process or thelike, by checking the presence or absence, the color and unevenness ofthe structural color, it is possible to easily confirm and control theformation of a desired primer layer. That is, after the primer layerformation, a primer layer forming state is controlled by producing thedesired structural color on the surface of the primer layer.

(4-4) Formation of Parting Layer 2C

The fluorocarbon polymer for the parting layer 2C used in the presentinvention is the crystalline fluorocarbon polymer and is insoluble inthe solvent. For that reason, the fluorocarbon polymer is used in theform of a dispersion of fluorocarbon polymer fine particles (primaryparticle size: 830 μm or less, preferably 360 nm or less) in the solventsuch as water. Incidentally, herein, the value of the primary particlesize refers to a measured value by the SEM. In the present invention, ofthe fluorocarbon polymers, it is possible to use the fluorocarbonpolymer having particularly high heat resistance and durability.Generally, the high heat-resistant fluorocarbon polymer has the highdurability and can be used when the fluorocarbon polymer has the meltingpoint of 250° C. or more and it is desirable that good durability can beobtained when the crystalline fluorocarbon polymer having the meltingpoint of 300° C. or more is used. As the applying method of thefluorocarbon polymer dispersion for the parting layer, a method offorming an unbaked smooth fluorocarbon polymer layer with less surfaceunevenness by leveling the dispersion on the roller surface may be used.Particularly, spray coating is preferred from the viewpoint of ease ofhandling but dipping can also be used, the unbaked fluorocarbon polymerlayer to be formed as the parting layer 2C is liable to be crackedduring drying or baking after the coating with an increasing thicknessof the coating. On the other hand, with a decreasing thickness of thecoating, the leveling of the dispersion is less liable to be performedduring the coating, so that spots are liable to occur. The thickness ofthe coating may desirably be in the range of 4 μm or more and 30 μm orless. One of features of the coating method is that the primer layer 2Dis a very thin layer and has a small unevenness and therefore thesurface of the parting layer 2C can be made very smooth whilesuppressing thermal deterioration of the rubber of the elastic layer 2B.Particularly, this effect is noticeable with the decreasing thickness ofthe coating, so that a very good surface can be formed even when thethickness of the parting layer 2C is 15 μm or less. Generally, when thethickness of the parting layer 2C is 15 μm or less, the state of theprimer layer 2D is liable to appear. On the other hand, with anincreasing thickness of the parting layer 2C from 15 μm, by a levelingaction of the parting layer itself, the influence of the parting layer2C on the surface of the underlying primer layer 2D is graduallyalleviated and thus becomes inconspicuous.

A baking means for baking the unbaked fluorocarbon polymer layer to beformed as the parting layer 2C may only be required to heat the unbakedfluorocarbon polymer layer to a temperature which is at least not lessthan the melting point of the fluorocarbon polymer. Examples of thebaking means may include an electric oven for circulating hot air, aninfrared heater for effecting radiation heating, and a means for bakingthe unbaked fluorocarbon polymer layer by locally creatinghigh-temperature air through a cylinder-like or coil-like heatgenerating element and then by passing the layer through the locally hotair. However, the elastic layer 2B underlying the parting layer 2Cgenerally does not have the heat resistance like that of thefluorocarbon polymer, so that the baking means and a baking method arerequired to be performed in a manner such that the film-forming propertyof the parting layer and minimization of deterioration of the elasticmember.

As the elastic member for the elastic layer 2B excellent in heatresistance, the addition curing silicone rubber frequently used for thefixing roller may be used but the heat-resistant temperature thereof isgenerally about 250° C. The melting point of the fluorocarbon polymerused for the fixing roller in this embodiment may be 250° C. or more,preferably 300° C. or more. Further, the baking is generally performedat a temperature which is higher than the melting point by 30° C. to 50°C., so that the deterioration of the elastic member cannot be avoidedalthough a degree thereof is different, and therefore there is a need toemploy a manufacturing method in which the deterioration is minimized.The baking may preferably be performed for 7 minutes or less as a timeat which the temperature is not less than the melting point of thecrystalline fluorocarbon polymer of the parting layer described above.

A significant feature of the present invention is that theabove-described fluorocarbon polymer dispersion which has the high heatresistance and high durability and is insoluble in the solvent is usedas the primer on the elastic layer 2B. Further, in the case where theparting layer 2C of the above-described fluorocarbon polymer which hasthe high heat resistance and high durability and is insoluble in thesolvent is formed, a high parting property and a high smoothness can beobtained while baking the parting layer 2C so that the influence on theelastic layer 2B is small. According to the constitution andmanufacturing method of the present invention, the thickness itself ofthe primer layer 2D is 830 nm or less, i.e., is not more than thevisible light wavelength (region), so that the resultant surfaceunevenness is also not more than 830 nm. For this reason, the primerlayer 2D which is very smooth and is free from a crack can be formed.For that reason, the parting layer 2C to be formed on the primer layer2D can be formed very smoothly at its surface already in a state beforethe baking. Also during the baking the underlying primer layer 2D is avery thin layer. For that reason, even when the crack is generated inthe primer layer 2D, a step height thereof is not more than (the lowerlimit of) the visible light wavelength, so that it is possible to form avery smooth film with no influence on the surface gloss and withoutlargely disturbing the surface smoothness.

(5) Advantages of Present Invention

In general, the fluorocarbon polymer primer does not contain a bindercomponent, for the purpose of preventing the mud crack during the dryingand the baking, in a large amount. This is because when the amount ofthe binder component is large, an amount of a substance which isvaporized during the baking is increased and trapped by the partinglayer on the primer layer and therefore the binder component adverselyaffects the film-forming property and impairs the bonding property. Thefluorocarbon polymer primer dispersion which does not contain the bindercomponent in the large amount is liable to cause the mud crack curingthe drying. Particularly, when the dispersion is coated uniformly on theelastic member so as to effect leveling in a so-called wet state (inwhich the dispersion is not dried soon on the elastic member), the crackoccurs easily during the drying. When the parting layer 2C in a state inwhich the mud cracks occur during the drying (FIG. 4( a)) is coated(FIG. 4( b)) and then baked, as schematically illustrated in FIG. 4( c),the cracks are enlarged by the influence of expansion of the basematerial 2A and the elastic layer 2B during the baking, so that theparting layer surface is largely roughened. As a coating method forpreventing the occurrence of the mud crack during the drying, a generaldry coating in spray coating, i.e., a method in which paint particles ofthe fluorocarbon polymer primer dispersion to be blown with a spray aremade small to facilitate drying thereof after being deposited on theelastic layer surface may be used. Further, it is also possible to use amethod in which the elastic member is heated and the fluorocarbonpolymer dispersion is applied so that the paint particles are driedimmediately after being deposited on the elastic member and thus smallpaint particles (FIG. 3( c)) are laminated. However, in general, in thespray coating method, the paint particles can be made small abut cannotbe formed in a size of less than 1 μm, so that as shown in FIGS. 3( b)and 3(c), the paint particles have an outer size of 5 μm to several tensof microns and a thickness of about 2 μm already after the paintparticles are deposited and dried on the surface of the elastic layer2B. FIG. 3( b) is the SEM photograph showing a state of the primer layerformed by the dry coating (a state in which the paint particles arefixed and laminated without being leveled. FIG. 3( c) is the SEMphotograph showing the state of the primer layer formed by the drycoating (enlarged fixed paint particles). The primer layer laminated onthe elastic layer 2B by being repeatedly coated on the elastic layer 2Bso as to cover at least the entire surface area of the elastic layer 2Bhas a final thickness of 4-6 μm (FIG. 5( a)). Further, the surface statethereof is, as shown in FIG. 3( b), such a roughened state that a largeamount of the surface unevenness is present due to the shape of thefixed paint particles. In the case where the primer layer has thesurface unevenness as described above, the surface of the parting layer2C on the primer layer 2D is influenced by the surface unevenness of theprimer layer, thus being liable to have an uneven surface (FIG. 5( b)).

As described above, there are the case where the parting layer surfaceis disturbed by progression of the crack in the primer layer during thebaking and the case where the surface of the unbaked parting layer (theparting layer after the drying) is not smooth due to the surfaceunevenness of the primer layer. In these cases, in order to obtain goodsurface property and gloss, the fluorocarbon polymer for the partinglayer is baked at a higher temperature or for a longer time. As aresult, the fluorocarbon polymer is sufficiently melted and leveled andthus the parting layer surface is required to be smoothened. However, inthis case, it is considerably feared that the underlying elastic layeris thermally deteriorated.

On the other hand, in the present invention, when the primer layer 2Ditself has a very smooth surface and is thin (FIG. 6( a)), the unbakedparting layer surface itself (after the drying) has already been verysmooth and good in property (FIG. 6( b)). Further, the primer layer 2Dis very thin and does not readily cause the crack, so that the crack isalso not readily generated in the parting layer itself during the bakingand therefore the parting layer surface is not largely disturbed duringthe baking. Therefore, it is possible to obtain a very good smoothsurface in the present invention without particularly making the bakingtemperature high or performing the baking for a long time, i.e., withoutsufficiently softening and melting the parting layer during the bakingso as to be sufficiently leveled. Further, as a result, the thermaldeterioration of the elastic layer during the baking can be suppressed.Thus, even when the fluorocarbon polymer of a high melting point gradesuch that the leveling is not readily performed and the melting point is310° C. or more is used as the fluorocarbon polymer for the partinglayer 2C, the good smooth surface can be formed easily. Further, thefluorocarbon polymer having the melting point of 310° C. or more has theespecially good heat resistivity and durability among the fluorocarbonpolymers, so that the present invention is also characterized in thatthe parting layer 2C which has the good surface property and has thegood heat resistivity and durability. Further, the present invention isparticularly suitable for the case where a total thickness of the primerlayer 2D and the parting layer 2C is 15 μm or less. This is because theunevenness of the primer layer is conspicuous as the surface unevennessof the parting layer with a smaller thickness of the parting layer. Inthe present invention, the primer layer 2D has the thickness of 830 nmor less and thus is very thin and smooth, so that the conspicuousunevenness cannot be created and thus a good film can be formed with noproblem even when the thickness of the parting layer 2C is small.

Further, with respect to the rotatable fixing member in which the heatis transferred between the elastic layer and the parting layer surface,the layer thickness on the elastic layer, i.e., the fixability isdisadvantageous as the total thickness of the primer layer and theparting layer is larger. Further, as the primer layer thickness and theparting layer thickness approaches each other, in the constitution ofthe rotatable fixing member, tolerances of both of the thicknessesinfluence the fixability, so that a variation in fixability is liable tooccur. On the other hand, in the constitution of the present invention,with respect to the primer layer thickness, the parting layer thicknessis substantially different by several tens of times to several hundredsof times, so that the primer layer thickness itself is less liable tocause a problem. Therefore, the tolerance of the primer layer thicknessis substantially negligible and thus the layer thickness on the elasticlayer is within the variation caused by substantially only the toleranceof the parting layer, so that a stable fixability can be ensuredcompared with the case where the primer layer is formed in a largethickness.

(6) Primer Layer Thickness Measuring Method

The primer layer thickness immediately after the primer layer formationcan be measured directly by using a laser scanning microscope or theSEM. Further, even after the baking, the thickness of the primer layer2D can be verified by using the following method. For example, across-sectional sample is analyzed by TOF-SIMS (time of flight secondaryion was spectrometer, so that a molecular structural difference betweenthe fluorocarbon polymers of the primer layer and the parting layer isdetected to check the thickness of the primer layer 2D. With respect tothe molecular structural difference, the primer has the functional groupas described above and thus the presence or absence of the functionalgroup may be checked and it is also possible to check the difference byeffecting mapping as a difference in fluorocarbon polymer itself, adifference in monometer structure, a difference in structure or numberof side chain, and the like. Further, as another method, e.g., thecross-sectional sample is prepared and then the molecular structuraldifference can be observed by measuring a component intrinsic to theprimer layer or the parting layer through elemental analysis using atransmission electron microscope (TEM) or the SEM. Further, as a simplenon-destructive inspection, it is possible to use an attenuated totalreflection method in which a crystal having a known analysis depth ispressed against the roller surface and a change in infrared (IR)spectrum due to the molecular structural difference between the primerlayer and the parting layer while checking a penetration length of thecrystal.

(7) Examples of Embodiment 1

Specific examples of the fixing film 2 which is the rotatable fixingmember in Embodiment 1 will be described.

(7-1) Fixing Film Manufacturing Method in Examples 1 to 3

The fixing films in Examples 1 to 3 have the same constitution exceptfor their thicknesses.

(7-1-1) Preparation of Elastic Layer for Fixing Film

As the base material 2A, an SUS metal belt (flexible endless beltmember) having a length of 240 mm, a thickness of 40 μm and an outerdiameter of 30 mm was used. On an outer circumferential surface of thebase material 2A<a primer (“DY39-051”, mfd. by Dow Corning Toray Co.,Ltd.) was uniformly coated in a thin layer in an area of 230 mm inlength. Then, the resultant structure was placed in an electric oven andwas dried at 200° C. for 30 min. As a material for the elastic layer 2B,a high heat-resistant silicone rubber (“SE4400”, mfd. by Dow CorningToray Co., Ltd.) which contained a heat-conductive filler in advance andhad thermal conductivity of about 1 W/m·k was used. This silicone rubberwas coated on the primer application area (300 μm in thickness and 230mm in length) on the base material 2A by the ring coating method (FIG.2( b)) to form a film and then the film was subjected to primaryvulcanisation at the surface temperature of 140° C. for 10 minutes bythe infrared heater while rotating the roller. Next, by baking thevulcanized silicone rubber at 200° C. for 4 hours, secondaryvulcanization was performed while bonding the cylindrical siliconerubber to the SUS metal belt (base material).

(7-1-2) Formation of Primer Layer for Fixing Film

Next, the surface of the elastic layer 2B formed on the SUS metal belt2A was subjected to UV treatment. This UV treatment is not essential butby the UV treatment, the tacking property of the silicone rubber surfaceis lowered and the water repellency of the silicone rubber surface ischanged into a hydrophilic property, so that a subsequent decrease inthickness of the primer layer and formation of the parting layer becomeeasy. After the UV treatment was performed, of the materials for thefluorocarbon polymer described above, the fluorocarbon polymer havingthe phosphoric group and the primary particle size of 150 nm was usedand dispersed in water and the resultant dispersion was coated on theelastic layer 2B. That is, this step is a first step of forming adispersion application layer by applying the dispersion of thefluorocarbon polymer mixture onto the elastic layer 2B. Then, theapplication layer was dried by hot air with a drier to form an about 4μm-thick layer in which mud cracks were generated. That is, this step isa second step of forming a dried primer layer by drying the dispersionapplication layer. Next, most of the primer layer is scraped off bypressing the non-woven fabric (“BEMCOT”) against the primer layersurface while rotating the belt on which the dried primer layer obtainedin the second step, so that the dried primer layer can be changed into auniform thin layer. That is, this step is a third step of decreasing thethickness of the dried primer layer by removing a part of the driedprimer layer.

The primer is constituted by spherical fixing device fine particleshaving the primary particle size of about 150 nm, so that the primerfine particles are liable to pass through a gap between the pressednon-woven fabric and the silicone rubber elastic layer. Further, theprimer fine particles present at an interface of the silicone rubber arephysically and chemically adsorbed by the silicone rubber surface, sothat the primer fine particles are not readily scraped off and thereforeare little removed by a manner of rubbing the primer fine particlesseveral times with the non-woven fabric while pressing the non-wovenfabric against the primer fine particles. However, the particle layer onthe layer constituting the interface is not largely influenced by thesilicone rubber, so that the particle layer is liable to be removed morethan the interfacial particle layer. As a result, it is possible to formthe primer layer which is an ultrathin layer (substantially singleparticle layer of 150 nm in thickness) principally comprising fineparticles substantially present at the interface of the primer layerwith the elastic layer 2B of the silicone rubber. Further, at the entiresurface of the primer layer on the elastic layer 2B, it was confirmedthat clear blue structural color appears uniformly by the thin primerlayer.

(7-1-3) Coating of Parting Layer for Fixing Film

Next, on the above-treated (ultrathin) primer layer, a PFA dispersion isspray-coated as the parting layer 2C. As the PFA dispersion, adispersion of PFA (“HP350” (primary particle size: about 160 nm), mfd.by Du Pont-Mitsui Fluorochemicals Co., Ltd.) in water is used and iscoated by a spray. In this case, by adjusting an application amount andthe number of reciprocation, the coating was made so that the surfacewas wet, i.e., was sufficiently leveled until it was dried. The coatingwas effected so that the parting layer had a thickness, including theprimer layer thickness, of 5 μm in Example 1, 8 μm in Example 2 and 15μm in Example 3.

(7-1-4) Baking of Parting Layer for Fixing Film

The fixing film after being subjected to the parting layer coating wasdried at 90° C. for 10 minutes, pre-heated at 220° C. for 30 minutes,and placed in an electric oven kept at 350° C., and then was baked for 7minutes, followed by air-cooling. As a result, three fixing films ofExample 1 (parting layer thickness: 5 μm), Example 2 (parting layerthickness: 8 μm) and Example 3 (parting layer thickness: 15 μm) inEmbodiment 1 were obtained.

(7-2) Comparative Embodiments

In order to substantiate the effect of the present invention,comparative embodiments in which the primer layer application manner andthe form of the primer layer and the parting layer are different fromEmbodiment 1 are shown below.

(7-2-1) Comparative Embodiment 1 and Comparative Embodiment 2

The manufacturing method of fixing films of Comparative Embodiment 1 andComparative Embodiment 2 are identical to that in Embodiment 1 exceptfor a manner of formation of the primer layer. Further, the fixing filmsof Comparative Embodiments 1 and 2 are only different in parting layerthickness. Until the UV treatment, the same process as in Examples 1 to3 in Embodiment 1 was performed and the primer layer was coated by drycoating in place of the wet coating. That is, when the primer is coatedby the spray, an end opening of a spray gun was narrowed by adjustingspraying pressure and a needle position to decrease a size of the spraycoating particles. Further, a deposition amount on the roller surfaceper ½ of reciprocation was decreased so that the spray coating particleswere not leveled with each other and were fixed on the elastic layersurface in a state in which graininess was retained (in a state in whichthe spray coating particles reached the elastic layer surface) when thespray coating particles were deposited on the roller surface. As aresult, the primer layer was formed in a thickness of about 4 μm in astate in which the spray coating particles of the fluorocarbon polymerprimer dispersion were stacked as shown in FIG. 3( b). The primer layerwas not subjected to the removal step, and then the parting layer wasformed in the same manner as in Embodiment 1 so that the (total)thickness of the parting layer (including the primer layer thickness)was 8 μm (Comparative Embodiment 1) and 15 μm (Comparative Embodiment2). Further, after the parting layer was coated, the baking and theair-cooling were also performed in the same manner as in Embodiment 1 toobtain a fixing film of Comparative Embodiment 1 (total thickness: 8 μm)and a fixing film of Comparative Embodiment 2 (total thickness: 15 μm).

(7-2-2) Comparative Embodiment 3

The manufacturing method of a fixing film of Comparative Embodiment 3 isidentical to that of Comparative Embodiment 2 except for the bakingmethod of the parting layer. That is, the fixing film after the dryingat 90° C. for 10 minutes and the pre-heating at 220° C. for 30 minuteswas placed in the electric oven kept at 360° C. and then was baked for10 minutes.

(7-2-3) Comparative Embodiment 4

The manufacturing method of a fixing film of Comparative Embodiment 4 isidentical to that of Comparative Embodiment 2 except for the bakingmethod of the parting layer. That is, the fixing film after the dryingat 90° C. for 10 minutes and the pre-heating at 220° C. for 30 minuteswas placed in the electric oven kept at 370° C. and then was baked for 7minutes.

(7-2-4) Comparative Embodiment 5

The manufacturing method of a fixing film of Comparative Embodiment 5 isidentical to that in Embodiment 1 except for a manner of formation ofthe primer layer. Until the UV treatment of the primer layer, the sameprocess as in Embodiment 1 was performed and the primer layer was coatedby the wet coating. That is, when the primer is coated by the spray, anend opening of a spray gun was increased by adjusting spraying pressureand a needle position to increase a size of the spray coating particles.Further, a deposition amount on the roller surface per ½ ofreciprocation was increased so that the spray coating particles werecoated and leveled with each other when the spray coating particles weredeposited on the roller surface. As a result, the primer layer wasformed in a thickness of about 4 μm but mud cracks occurred in theprimer layer as schematically illustrated in FIG. 4( a). The primerlayer was not subjected to the removal step, and then the parting layerwas formed in the same manner as in Embodiment 1 so that the (total)thickness of the parting layer (including the primer layer thickness)was 15 μm. Further, after the parting layer was coated, the baking wasalso performed in the same manner as in Embodiment 1 (Examples 1 to 3)to obtain a fixing film of Comparative Embodiment 5.

(8) Performance Comparison Between Examples in Embodiment 1 andComparative Embodiments

With respect to the above-prepared fixing films of Examples 1 to 3 inEmbodiment 1 and fixing films of Comparative Embodiments 1 to 5, surfaceproperties (surface unevenness, gloss feeling, presence or absence ofrubber blister) and an image gloss value (glossiness) when each of thefixing films was incorporated in the fixing device and a color image onthe recording material was heat-fixed were compared. The results areshown in Table 1.

TABLE 1 PRIMER PARTING BAKING IMAGE LAYER LAYER CONDITION SURFACE GLOSSGLOSS RUBBER EMB. NO. THICKNESS THICKNESS (° c./MIN.) STATE *1 FEELINGVALUE BLISTER *2 EMB. 1 EX. 1 150 nm 5 μm 350/7 A A 74 A EMB. 1 EX. 2150 nm 8 μm 350/7 A A 71 A EMB. 1 EX. 3 150 nm 15 μm  350/7 A A 65 ACOMP. EMB. 1 ca.4 μm dry 8 μm 350/7 C C 38 A COMP. EMB. 2 ca.4 μm dry 15μm  350/7 B B 50 A COMP. EMB. 3 ca.4 μm dry 8 μm  360/10 B B 53 B COMP.EMB. 4 ca.4 μm dry 8 μm 370/7 B B 55 C COMP. EMB. 5 ca.4 μm wet 15 μm 350/7 D D 35 A *1: “A” represents good, “B” represents that surfaceunevenness somewhat occurred, “C” represents that surface unevennessoccurred, and “D” represents that surface unevenness considerablyoccurred. *2: “A” represents that the rubber blister did not occur, “B”represents that the rubber blister slightly occurred, and “C”representsthat the rubber blister somewhat occurred.

In Table 1, the “surface state” is an observation result when thesurface of each of the fixing films is observed through an opticalmicroscope with 50-fold magnification. Further, the “gloss feeling” isevaluated relatively in four grades (A: Excellent, B: Good, C: Somewhatpoor, D: Poor) when the surface of each of the fixing films is observedby eyes. The “Glossiness (image gloss value)” is a measured gloss valueby a handy gloss meter (“PG-1” (at 75 deg.), mfd. by Nippon DenshokuIndustries Co., Ltd.) when a solid image of secondary color of blue isfixed on letter (LTR) paper. Further, the “rubber blister” is such aphenomenon that the elastic layer silicone rubber is decomposed byhigh-temperature thermal deterioration during baking to cause localswelling (blister).

From the results of Table 1, it is understood that good effects in termsof the surface properties are achieved in Examples 1 to 3 in Embodiment1 of the present invention. Particularly, compared with the case wherethe primer is dry-coated as in Comparative Embodiment 1, the bettersurface properties and the better gloss values are obtained in Examples1 to 3 in Embodiment 1. In this embodiment, even when the thickness ofthe parting layer is decreased, the surface smoothness is not loweredand the gloss value is not decreased. On the other hand, with respect tothe total thickness of 15 μm and 8 μm, in Comparative Embodiments 1 to5, the surface properties and the gloss values are lowered. Fromcomparison between Example 2 in Embodiment 1 and Comparative Embodiments3 and 4, in the case where the primer is coated by the dry coating, evenwhen the baking temperature is increased or the baking temperature isprolonged, the surface properties and the glass values in ComparativeEmbodiments 3 and 4 do not reach levels of Example 2 in Embodiment 1.Moreover, in Comparative Embodiments 3 and 4, the blister due to thethermal deterioration of the rubber has occurred. Further, inComparative Embodiment 5 in which the fixing film is prepared bywet-coating the primer, it is understood that the cracks occur at theprimer layer surface and both of the surface properties and the glossvalue are not good.

In Embodiment 1 of the present invention, the film heating type fixingdevice 114 is used as the fixing device and the fixing film 2 is used asthe rotatable fixing member. However, when only the base material forthe fixing film 2 is used as it is for a cylindrical rigid metal member,the base material can also be used as the fixing roller or the pressingroller for the fixing roller type fixing device. When the base materialis the cylindrical rigid metal member, the base material can be formedin the fixing roller or the pressing roller in which the heater isincorporated.

Embodiment 2 (2) Fixing Device 115

FIG. 7( a) is a schematic cross-sectional view of a principal part of afixing device 115 in Embodiment 2. This fixing device 115 is of aso-called surface heating type fixing device and as the fixing rollerfor the fixing device of this type, the rotatable fixing memberaccording to the present invention can be used. Referring to FIG. 7( a),a fixing roller 11 is the rotatable fixing member according to thepresent invention. An elastic pressing roller 12 is disposed below andin parallel to the fixing roller 11 and is pressed against the fixingroller 11 with a predetermined urging force by an unshown urging member.As a result, a fixing nip N2 with a predetermined width is createdbetween the fixing roller 11 and the pressing roller 12. A heating unit13 for externally heating the fixing roller 11 is disposed above and inparallel to the fixing roller 11. The heating unit 13 performs thefunction of applying heat from a ceramic heater 14 to the fixing roller11 through an endless film 15 in a heating nip N1. The ceramic heater 14is supported by a heater holder 16 and applies the urging force of about3 kgf to about 25 kgf in total pressure to the heater holder 16 througha U-like metal plate 17 by an unshown spring. As a result, the heatingunit 13 is pressed against the fixing roller 11 to create the heatingnip N1 with a predetermined width. Further, on a surface of the ceramicheater 14 opposite from the surface constituting the nip N1, athermistor (not shown) as a temperature detecting element is disposed incontact with the ceramic heater 14. On the basis of a detectedtemperature from this thermistor, electric power supply to the ceramicheater 14 is controlled, so that the temperature of the ceramic heater14 is controlled at a predetermined temperature. As a result, an amountof heat applied to the fixing roller 11 is always controlled.

The fixing roller 11 is rotationally driven in a clockwise directionindicated by an arrow at a predetermined speed by a motor (not shown)controlled by a control circuit portion (not shown) at least duringexecution of the image formation. The pressing roller 12 is rotated in acounterclockwise direction indicated by an arrow by the rotation of thefixing roller 11. Further, in the heating unit 13, by a frictional forcecreated in the heating nip N1 between the fixing roller 11 and the film15 by the rotation of the fixing roller 11, a rotational force acts onthe film 15. As a result, the film 15 is rotated around the holder 16 inthe counterclockwise direction indicated by the arrow at a peripheralspeed substantially corresponding to the rotational peripheral speed ofthe fixing roller 11 while intimately sliding on the surface of theheater 14 in the nip N1 at the inner surface of the film 15. Further,the heater 14 is increased in temperature by being supplied withelectric power from a power supply (not shown). The temperature of theheater 14 is detected by the thermistor. Detected temperatureinformation is fed back to the control circuit portion. The controlcircuit portion controls the electric power input from the power supplyto the heater 14 so that a detected temperature input from thethermistor 5 is kept at a predetermined target temperature (fixingtemperature). By the heat of this heater 14, the surface of the rotatingfixing roller 11 is externally heated through the film 15 in the heatingnip N1.

In a state in which the fixing roller 11 is rotationally driven and theheater 14 is heated and temperature-controlled at the predeterminedfixing temperature, the recording material P carrying thereon an unfixedtoner image T is introduced into fixing the nip N2 with a toner imagecarrying surface toward the fixing roller 11 side. e recording materialP intimately contacts the outer surface of the fixing roller 11 in thefixing nip N2 and is nip-conveyed in the fixing nip N2. As a result,heat of the fixing roller 11 is applied to the recording material P andthe pressing force is applied to the recording material P in the nip N2,so that the unfixed toner image T is thermally press-fixed on thesurface of the recording material P. The recording material P which haspassed through the nip N2 is self-separated from the outercircumferential surface of the fixing roller 11 and is conveyed to theoutside of the fixing device 115.

(2) Layer Structure of Fixing Roller 11

FIG. 7( b) is a schematic view showing a layer structure of the fixingroller 11. Although a specific constitution will be described below, theelastic layer for the fixing roller 11 consists of two layers which havedifferent functions. That is, on the circumferential surface of a coremetal 18 as the base material, a heat insulating elastic layer 19 as alayer having a heat insulating function is formed and thereon a heataccumulation layer 20 as a layer having a heat accumulation function isformed. The heat insulating elastic layer 19 has the function ofimparting elasticity to the roller 11 and insulates the heat applied tothe heat accumulation layer 20 to prevent the heat from escaping towardthe core metal 18 side. Further, the heat accumulation layer 20 isformed of the high heat-conductive silicone rubber and impartselasticity toward the neighborhood of the outermost surface of theroller 11. At the same time, the heat accumulation layer 20 canaccumulate the heat from the heating unit 13 by the high heat-conductivefiller in the high heat-conductive silicone rubber and has the functionof dissipating the heat onto the recording material P. On thecircumferential surface of the heat accumulation layer 20, a primerlayer 22 is formed and a parting layer 21 is formed on the primer layer22. The parting layer 21 is formed of a fluorocarbon polymer having agood parting property so that the toner T on the recording material Pcauses offset. The parting layer 21 may preferably have a thickness assmall as possible in order to facilitate heat conduction from theheating unit 13 to the heat accumulation layer 20 and conduction of heataccumulated in the heat accumulation layer 20 to the recording materialP and the toner T on the recording material P, thus being desirably 25μm or less as a total thickness of the primer layer 22 and the partinglayer 21.

That is, the fixing roller 11 is supplied with heat from the heatingunit 13 in the heating nip N1 and accumulates the heat in the heataccumulation layer 20 in the neighborhood of the surface layer. At thistime, the heat insulating elastic layer 19 performs the function ofpreventing the heat accumulated in the heat accumulation layer 20 fromescaping toward the core metal side. Then, the heater accumulated in theheat accumulation layer 20 is dissipated onto the recording material Pand the toner T thereon which are nip-conveyed in the fixing nip N2between the fixing roller 11 and the pressing roller 12, so that thetoner T can be fixed on the recording material P by heat and pressure.The fixing roller 11 may desirably have a hardness in the range of 35degrees to 60 degrees as measured by an ASKER-C hardness meter (load:500 gf) in order to obtain an appropriate nip width, and the elasticlayer (consisting of the heat insulating elastic layer and the heataccumulation elastic layer) may desirably have a thickness in the rangeof 1 mm to 5 mm. It is desirable that the pressing roller 12 is pressedagainst the fixing roller 11 with a total pressure of about 3 kgf toabout 25 kgf.

In the fixing device 115 of the external surface heating type, the totalthickness of the rubber layer (the sum of the thicknesses of the heatinsulating elastic layer 19 and the heat accumulation elastic layer 20)of the fixing roller 11 which is directly contactable to the toner T.For that reason, the fixing device 115 has sufficient elasticity and canfix the toner on the recording material while sufficiently covering thetoner by following the surface shape of the recording material even whenan unevenness due to paper fibers occurs at the surface of the recordingmaterial. As a result, it is possible to suppress density non-uniformitydue to non-uniformity of a degree of toner deformation and to suppresscolor mixing non-uniformity of the color toners. This effect of thefixing device 115 is remarkable compared with that of the fixing device114 in Embodiment 1.

In the fixing device 115 of the type, as the thickness of the partinglayer 21 is larger, the supply of the heat from the heating unit 13 tothe heat accumulation elastic layer 20 in the heating nip N1 and thedissipation of the heat from the heat accumulation elastic layer 20 ontothe recording material P are more prevented. As a result, the fixabilityis lowered and therefore it has desired that the parting layer is formedin a small thickness. However, particularly in the case where thethickness of the elastic layer underlying the parting layer 21 is largeas in this embodiment, compared with Embodiment 1 (in which the elasticlayer is thin), the influence of expansion of the elastic layer duringthe baking of the parting layer is large. For that reason, it has beenfurther difficult to form the parting layer with no adverse influencessuch as the lowering in surface properties, the lowering in durability,and the thermal deterioration of the elastic layer. According to thepresent invention, with no these adverse influences, the parting layer12 of the fixing roller 11 can be formed in the small thickness.

(3) Constitution of Fixing Roller 11

Next, the constitution of the fixing roller 11 will be described. Theconstitution of the fixing roller 11 is the same as that in Embodiment 1except for a part of the base material and the elastic layer.

(3-1) Base Material 18

As the base material 18, e.g., the core metal formed of metal such asaluminum, iron, stainless steel or nickel, or alloy of these metals.

(3-2) Elastic Layers 19 and 20

As a material for each of the heat insulating elastic layer 19 and theheat accumulation 20, e.g., a heat-resistant rubber such as a siliconerubber or a fluorocarbon rubber is used. Particularly, similarly as inEmbodiment 1, of the silicone rubber, an addition curing silicone rubberis frequently used from the viewpoint of a processing property. As theaddition curing silicone rubber for the elastic layer 19 used as theheat insulating layer, a solid rubber may be used as it is. In order topositively impart the heat insulating property to the elastic layer 19,a heat insulating filler may be mixed, or a rubber such as organic foamrubber, millable rubber, water-expanded foam rubber, which is excellentin heat insulating property and has the thermal conductivity in therange of 0.23 W/m·k to 0.1 W/m·k. The elastic layer 19 may desirablyhave a thickness of 1 mm or more and 5 mm or less in order to impart theelasticity for creating the fixing nip N2. In the conventional fixingdevice, the elastic layer having such a thickness is largely expandedwhen the coating parting layer is formed thereon (particularly duringthe baking of the coating), thus being remarkably disadvantageous interms of formation of the coating parting layer. However, according tothe present invention, a good parting layer can be formed. Further, therubber hardness may preferably be in the range from 0 degrees to 45degrees in terms of JIS-A hardness. Further, with respect to the elasticlayer 20 used as the heat accumulation layer, similarly as in the caseof the elastic layer in Embodiment 1, the silicone rubber in which thehigh heat-conductive filler is dispersed is used. As the highheat-conductive filler, it is possible to use alumina, aluminum nitride,boron nitride, carbon, carbon nanofiber, metal silicon, zinc oxide,silicon oxide, etc. These materials can be used singly or in mixture oftwo or more species. In order to obtain a sufficient heat accumulatingproperty, particularly, a high heat-conductive silicone rubber havingthe thermal conductivity of 0.7 W/m·k or more and 2.0 W/m·k or less maydesirably be used.

Further, with respect to the thickness of the heat accumulation elasticlayer 20, a heat, accumulation function is impaired when the thicknessis excessively small, and it is difficult to dissipate the accumulatedheat when the thickness is excessively large. Therefore, the heataccumulation layer 20 may desirably be formed in the thickness in therange of 0.05 mm to 1.0 mm, more desirably 0.08 mm to 0.2 mm.

(3-3) Primer Layer 22

Between the heat accumulation elastic layer 20 and the parting layer 21,the primer layer 22 for bonding the elastic layer 20 of the siliconerubber and the parting layer of the fluorocarbon polymer is provided.The material for the primer layer 22 is the same as that in Embodiment 1and thus a specific description will be omitted but is a thermallymelted product of a fluorocarbon polymer containing a crystallinefluorocarbon polymer having a functional group. An aqueous dispersion inwhich fine particles of a mixture of the crystalline fluorocarbonpolymer containing the functional group and a crystalline fluorocarbonpolymer containing no functional group are dispersed in an aqueoussolvent (water) is used. Incidentally, the primary particle size of thefine particles is also the same as that in Embodiment 1, i.e., isrequired to be 830 nm or less, preferably 360 nm or less. Further, thethickness of the primer layer 22 is also the same as that in Embodiment1, i.e., is required to be 830 nm or less, preferably 360 nm or less inorder to provide the parting layer 21 with good surface properties.

(3-4) Parting Layer 21

The fluorocarbon polymer for the parting layer 21 used in thisembodiment is the same as that in Embodiment 1. Therefore, detailsthereof will be omitted but a fluorocarbon polymer mixture containingthe crystalline fluorocarbon polymer which is insoluble in a solvent isused. For that reason, the fluorocarbon polymer is used in the form of adispersion of fluorocarbon polymer fine particles (primary particlesize: 830 μm or less, preferably 360 nm or less) in the solvent such aswater.

(4) Manufacturing Method of Fixing Roller 11 (4-1) Formation of ElasticLayers 19 and 20

On the base material 18 which has been treated with a primer in advance,the elastic layers 19 and 20 are formed. The elastic layers 19 and 20may be formed by a known method, such as a method in which the materialsuch as a liquid silicone rubber or the like is coated on the basematerial 18 in a uniform thickness by a means such as blade coating andthen is heat-cured. It is also possible to form the elastic layers 19and 20 by a method in which the material such as the liquid siliconerubber is injected into a mold and then is heat-cured, a method ofheat-curing the material after extrusion molding, a method ofheat-curing after ejection molding, and the like. In the case where anaddition curing liquid silicone rubber which exhibits a particularlygood heat insulating property and contains microballoons is used as thematerial for the elastic layer 19 as the heat insulating layer, thesilicone rubber may desirably be molded by using a mold so that a skinlayer can be formed. By the microballoons, many pores are formed in thethick elastic layer 19, so that the elastic layer 20 to be formed on theelastic layer 19 is roughened when the skin layer is not present. Theelastic layer 20 as the heat accumulation layer is formed by coating onthe elastic layer 19 the addition curing liquid silicone rubber mixture,in which alumina particles are mixed as the high heat conductive filler,by using the ring coating in the same manner as that in the case of theelastic layer 2B in Embodiment 1. Then, the coated silicone rubbermixture can be heat-cured by the primary vulcanization and then by thesecondary vulcanization to form the elastic layer 20.

(4-2) Pre-Process of Primer Layer Formation on Elastic Layer Surface

The surface of the elastic layer 20 which has been formed by completingthe secondary vulcanization may desirably be subjected to hydrophilizingtreatment through UV treatment (UV irradiation treatment) on the likebefore the primer layer 22 is formed similarly as in Embodiment 1.

(4-3) Formation of Primer Layer 22

In order to obtain good surface smoothness of the parting layer also inthis embodiment, the primer layer 22 is formed on the heat accumulationelastic is layer 20 similarly as in Embodiment 1. That is, the primerlayer 22 is required to be formed in a thickness of 830 nm or less,preferably 360 nm or less so as to cover the entire area of the elasticlayer 20. For that purpose, the method of forming the primer layer 22 onthe elastic layer 20 may desirably include at least three steps (Firstto third steps) described below. The first step is a step of applyingthe dispersion of the primer so as to cover the entire area of theelastic layer. Then, in the second step, the coating layer of the primerlayer is dried to obtain a dried primer layer. Then, in the third step,a part of the dried primer layer is removed to decrease and uniformizethe layer thickness to 850 nm or less.

(4-4) Formation of Parting Layer 21

The fluorocarbon polymer primer and the fluorocarbon polymer for theparting layer 21 which are used in the present invention are insolublein the solvent similarly as in Embodiment 1. For that reason, thefluorocarbon polymer primer is used in the form of a dispersion offluorocarbon polymer primer fine particles (primary particle size: 850μm or less) in the solvent such as water. Incidentally, herein, thevalue of the primary particle size refers to a measured value by theSEM. In the constitution of this embodiment, the thickness of theelastic layer may desirably be 1 mm or more and 5 mm or less, which islarger than that of the elastic layer in the constitution of Embodiment1 by several times to several tens of times, so that an amount ofthermal expansion is also large. In this case, when the primer layer 22is formed in a large thickness, large cracks are liable to occur duringthe baking. However, in this embodiment, the thickness itself of theprimer layer 22 is 850 nm or less, so that the resultant surfaceunevenness is also not more than 850 nm. For this reason, the primerlayer 22 which is very smooth and is free from a crack can be formed.For that reason, the parting layer 21 to be formed on the primer layer2D can be formed very smoothly at its surface already in a state beforethe baking. Also during the baking the underlying primer layer 2D is avery thin layer. For that reason, there is no influence of theoccurrence of the crack and it is possible to form a very smooth filmwithout largely disturbing the surface smoothness.

(5) Advantages of Present Invention

For this reason, in the present invention, even in the case where thethermal expansion of the roller outer shape is large during the bakingof the parting layer, it is possible to form the film having the verygood surface properties. Particularly, even in the case where theelastic layer has a large thickness and the large thermal expansionamount, specifically in the case where the elastic layer has a thicknessof more than 1 mm, the very good parting layer can be formed in thefilm.

(6) Primer Layer Thickness Measuring Method

The primer layer thickness immediately after the primer layer formationcan be measured in the same manner as in Embodiment 1.

(7) Fixing Roller in Embodiment 2

A manufacturing method of the fixing roller 11 shown in FIG. 7( b) asthe fixing roller in Embodiment 2 will be described based on specificexamples.

(7-1) Preparation of Elastic Layer 19 (Heat Insulating Layer) for FixingRoller 11

As the base material 18, a core metal of aluminum having an outerdiameter of 10 mm was used. On the other circumferential surface of thecore metal 18, a primer (“DY39-051”, mfd. by Dow Corning Toray Co.,Ltd.) was uniformly coated in a thin layer and then was baked at 200° C.for 30 min. The thus primer-treated core metal 18 was set in a pipe-likemetal mold. Then, into the metal mold, as the silicone rubber for theelastic layer 19, a well-mixed composition (mixture) of the additioncuring silicone rubber containing resinous microballoons withtriethylene glycol as an open cell-forming agent was injected and wassubjected to the primary vulcanization at 130° C. for 60 min. As aresult, a cylindrical elastic layer 19 having a thickness of 3.0 mm, alength of 230 mm, and an outer diameter of 15.9 mm with the skin layeras the outermost surface layer was formed by molding.

(7-2) Preparation of Elastic Layer 20 (Heat Accumulation Layer) forFixing Roller 11

On the above-formed elastic layer 19, similarly as in Embodiment 1, theelastic layer 20 of the high heat-conductive filler-containing siliconerubber by the ring coating method. As the high heat-conductivefiller-containing silicone rubber, an addition curing silicone rubber(“SE4400”, mfd. by Dow Corning Toray Co., Ltd.) which contained analumina filler was used. This silicone rubber was coated on the elasticlayer 19 in a thickness of 100 μm by the ring coating method (FIG. 2(b)) and was subjected to the primary vulcanization at 130° C. for 5minutes by the infrared heater. Therefore, the high heat-conductivefiller-containing silicone rubber is cured by being heated for 4 hoursin the electric oven set at 200° C. to form the elastic layer 20.

(7-3) Formation of Primer Layer 22 for Fixing Roller 11

Next, the surface of the elastic layer 20 was subjected to UV treatment(UV irradiation). Then, on the surface of the elastic layer 20, afluorocarbon polymer primer which was the same aqueous dispersion asthat in Embodiment 1 was spray-coated. That is, this step is a firststep of forming a dispersion application layer by applying thedispersion of the fluorocarbon polymer mixture onto the elastic layer20. Then, the application layer was dried by hot air with a drier toform an about 4 to 6 μm-thick dried primer layer in which mud crackswere generated. That is, this step is a second step of forming a driedprimer layer by drying the dispersion application layer. Next, thenon-woven fabric (“BEMCOT”) was pressed against the primer layer surfacewhile rotating the roller on which the dried primer layer obtained inthe second step, so that a part of the dried primer layer was removed.That is, this step is a third step of decreasing the thickness of thedried primer layer by removing a part of the dried primer layer.

The primer is constituted by spherical fixing device fine particleshaving the primary particle size of about 150 nm, so that the primerfine particles are liable to pass through a gap between the pressednon-woven fabric and the surface of the elastic layer 20. Further, theprimer fine particles present at an interface of the silicone rubber arephysically and chemically adsorbed strongly by the silicone rubbersurface, so that the primer fine particles are not readily scraped offand therefore are little removed by a manner of rubbing the primer fineparticles with the non-woven fabric while pressing the non-woven fabricagainst the primer fine particles. By changing the thickness of thedried primer layer and the degree of the pressing with the non-wovenfabric, most of the primer layer can be uniformly scraped off to adjustthe layer thickness, so that the primer layers having thicknesses of 150nm, 450 nm and 800 nm were formed.

(7-4) Formation of Parting Layer for Fixing Roller 11

As the material for the parting layer, a dispersion of PFA fineparticles having the melting point of 310° C. and the particle size of200-300 nm. Was used. This dispersion was coated on the roller surfaceby spray coating. The parting layer was formed so that the totalthickness including the primer layer thickness was 8 μm and 15 μm. Atthis time, the dispersion was set-coated by the spray coating so as tobe leveled on the roller surface. Then, the roller coated with theparting layer was placed and dried for 10 minutes in the electric ovenset at 90° C. and then baked for 7 minutes in the electric oven set at360° C. Then the roller was taken out and then was air-cooled.

In the above-described manner, six fixing rollers in Examples 1 to 6 ofEmbodiment 2 in which the primer layer thickness was 150 nm, 450 nm or800 nm and the total thickness including the primer layer thickness was8 μm or 15 μm were prepared. Specifically, the fixing roller in Example1 had the primer layer thickness of 800 nm and the total thickness of 15μm, the fixing roller in Example 2 had the primer layer thickness of 450nm and the total thickness of 15 μm, the fixing roller in Example 3 hadthe primer layer thickness of 150 nm and the total thickness of 15 μm,the fixing roller in Example 4 had the primer layer thickness of 800 nmand the total thickness of 8 μm, the fixing roller in Example 5 had theprimer layer thickness of 450 nm and the total thickness of 8 μm, andthe fixing roller in Example 6 had the primer layer thickness of 150 nmand the total thickness of 8 μm. In this embodiment, the heataccumulation elastic layer 20 was formed by the ring coating method butmay also be formed by a method in which a silicone rubber which has beenmolded in advance by, e.g., an extruding machine is coated on the baseelastic layer 19 or by a beam coating method. Further, the fluorocarbonpolymer primer dispersion is coated on the elastic layer 20 by the spraycoating method but may also be coated by a dipping method or the like.

Further, the fluorocarbon polymer dispersion for the parting layer 21 iscoated by the spray coating method but may also be coated by the dippingmethod.

(8) Comparative Embodiments

In order to substantiate the effect in Embodiment 2 of the presentinvention, comparative embodiments in which the primer layer applicationmanner and the form of the layer and the baking method are changed areshown below.

(8-1) Comparative Embodiment 1 and Comparative Embodiment 2

The manufacturing method of fixing rollers of Comparative Embodiment 1and Comparative Embodiment 2 are identical to that in Embodiment 2except for a method of formation of the primer layer. First, until theUV treatment, the same process as in the case of the fixing roller inEmbodiment 2 was performed. The primer layer was coated by the drycoating described above. That is, when the primer is coated by thespray, an end opening of a spray gun was narrowed by adjusting sprayingpressure and a needle position. As a result, a size of the spray coatingparticles was decreased. Further, a deposition amount on the rollersurface per ½ of reciprocation was decreased so that the spray coatingparticles were not leveled with each other and were fixed on the rollerlayer surface in a coating grain state when the spray coating particleswere deposited on the roller surface. As a result, the primer layer wasformed in a thickness of about 5 μm in a state in which the primercoating grains were stacked as shown in FIG. 3( b). The primer layer wasnot subjected to the removal step, and then the parting layer was formedin the same manner as in the case of the fixing roller 11 in Embodiment2 so that the total thickness of the parting layer (including the primerlayer thickness) was 15 μm and 8 μm. Further, the baking of the partinglayer was also performed in the same manner as in Embodiment 2 to obtaina fixing roller of Comparative Embodiment 1 and a fixing roller ofComparative Embodiment 2.

(8-2) Comparative Embodiment 3 and Comparative Embodiment 4

The manufacturing method of fixing rollers of Comparative Embodiment 3and Comparative Embodiment 4 are identical to that in ComparativeEmbodiment 1 and Comparative Embodiment 2 except for the primer layerthickness. The primer layer was formed by the dry coating, so that theprimer layer thickness was 3 μm. The primer layer was not subjected tothe removal step, and then the parting layer was coated so that thetotal thickness of the parting layer (including the primer layerthickness) was 15 μm and 8 μm. The baking of the parting layer wasperformed in the same manner as in Comparative Embodiments 1 and 2 toobtain a fixing roller of Comparative Embodiment 3 and a fixing rollerof Comparative Embodiment 4.

(8-3) Comparative Embodiment 5 and Comparative Embodiment 6

The manufacturing method of fixing rollers of Comparative Embodiment 5and Comparative Embodiment 6 are identical to that in ComparativeEmbodiment 1 and Comparative Embodiment 2 except for the primer layerthickness and the primer layer forming method. The primer layer wasformed by the wet coating. That is, when the primer is coated by thespray, an end opening of a spray gun was increased by adjusting sprayingpressure and a needle position. As a result, a size of the spray coatingparticles was increased. Further, a deposition amount on the rollersurface per ½ of reciprocation was increased so that the spray coatingparticles were leveled with each other. As a result, the primer layerwas formed in a thickness of about 3 μm. The primer layer was subjectedto the removal step in the same manner as in Embodiment 2 and thepressure of the pressing member was adjusted to decrease the thicknessto 1 μm. The primer layer was not subjected to the removal step, andthen the parting layer was coated so that the total thickness of theparting layer (including the primer layer thickness) was 15 μm and 8 μm.The baking of the parting layer was performed in the same manner as inComparative Embodiments 1 and 2 to obtain a fixing roller of ComparativeEmbodiment 5 and a fixing roller of Comparative Embodiment 6.

(8-4) Comparative Embodiment 7 and Comparative Embodiment 8

The manufacturing method of fixing rollers of Comparative Embodiment 7and Comparative Embodiment 8 are identical to that in ComparativeEmbodiment 1 and Comparative Embodiment 2 except for the primer layerthickness and the primer layer forming method. The primer layer wasformed by the wet coating. That is, when the primer is coated by thespray, an end opening of a spray gun was increased by adjusting sprayingpressure and a needle position to increase a size of the spray coatingparticles. Further, a deposition amount on the roller surface per ½ ofreciprocation was increased so that the spray coating particles werecoated and leveled with each other when the spray coating particles weredeposited on the roller surface. As a result, the primer layer wasformed in a thickness of about 5 μm but mud cracks occurred in theprimer layer as schematically illustrated in FIG. 4( a). The primerlayer was not subjected to the removal step, and then the parting layerwas formed in the same manner as in Embodiment 2 so that the totalthickness of the parting layer (including the primer layer thickness)was 15 μm and 8 μm. Further, the baking of the parting layer was alsoperformed in the same manner as in Embodiment 2 to obtain a fixingroller of Comparative Embodiment 7 and a fixing roller of ComparativeEmbodiment 8.

(8-5) Comparative Embodiment 9

The manufacturing method of fixing roller 9 of Comparative Embodiment 9is identical to that in Comparative Embodiment 1 except for the bakingmethod. The primer layer was formed by the dry coating, so that theprimer layer thickness was 3 μm. The primer layer was not subjected tothe removal step, and then the parting layer was coated so that thetotal thickness of the parting layer (including the primer layerthickness) was 15 μm. The baking of the parting layer was performed byplacing the roller in the electric furnace and by being dried at 90° C.for 10 min., pre-heated at 220° C. for 30 min., and baked at 360° C. for8 min. Then, the roller was taken out from the electric furnace and wasair-dried to obtain a fixing roller of Comparative Embodiment 9.

(8-6) Comparative Embodiment 10

The manufacturing method of fixing roller 9 of Comparative Embodiment 10is identical to that in Comparative Embodiment 1 except for the bakingmethod. The primer layer was formed by the dry coating, so that theprimer layer thickness was 3 μm. The primer layer was not subjected tothe removal step, and then the parting layer was coated so that thetotal thickness of the parting layer (including the primer layerthickness) was 15 μm. The baking of the parting layer was performed byplacing the roller in the electric furnace and by being dried at 90° C.for 10 min., pre-heated at 220° C. for 30 min., and baked at 380° C. for8 min. Then, the roller was taken out from the electric furnace and wasair-dried to obtain a fixing roller of Comparative Embodiment 10.

(9) Performance Comparison Between Examples 1-6 in Embodiment 2 andComparative Embodiments 1-10

With respect to the above-prepared fixing rollers of Examples 1 to 6 inEmbodiment 2 and fixing rollers of Comparative Embodiments 1 to 10,surface properties (surface unevenness, gloss feeling, thermaldeterioration of rubber) and an image gloss value (glossiness) when eachof the fixing rollers was incorporated in the fixing device and a colorimage on the recording material was heat-fixed were compared. Theresults are shown in Table 2.

TABLE 2 TYPE OF PFA IN PRIMER BAKING IMAGE PARTING LAYER TOTAL CONDITIONSURFACE GLOSS GLOSS RUBBER EMB. NO. LAYER THICKNESS THICKNESS (°C./MIN.) STATE *1 FEELING VALUE BLISTER *2 EMB. 2 EX. 1 HMP *3 800 nm 15μm 360/7 A A 70 A EMB. 2 EX. 2 HMP 450 nm 15 μm 360/7 A A 71 A EMB. 2EX. 3 HMP 150 nm 15 μm 360/7 A A 77 A EMB. 2 EX. 4 HMP 800 nm  8 μm360/7 A A 70 A EMB. 2 EX. 5 HMP 450 nm  8 μm 360/7 A A 71 A EMB. 2 EX. 6HMP 150 nm  8 μm 360/7 A A 77 A COMP. EMB. 1 HMP 5 μm 15 μm 360/7 C C 56A COMP. EMB. 2 HMP 5 μm  8 μm 360/7 C C 44 A COMP. EMB. 3 HMP 3 μm 15 μm360/7 C C 56 A COMP. EMB. 4 HMP 3 μm  8 μm 360/7 C C 44 A COMP. EMB. 5HMP 1 μm 15 μm 360/7 C C 58 A COMP. EMB. 6 HMP 1 μm  8 μm 360/7 C C 46 ACOMP. EMB. 7 HMP 5 μm wet 15 μm 360/7 C D 40 A COMP. EMB. 8 HMP 5 μm wet 8 μm 360/7 C D 37 A COMP. EMB. 9 HMP 5 μm 15 μm 360/8 B B N.M. *4 BCOMP. EMB. 10 HMP 5 μm 15 μm 360/8 B A N.M. *4 C *1: “A” representsgood, “B” represents that surface unevenness somewhat occurred, and “C”represents that surface unevenness occurred. *2: “A” represents thatabnormal hardness and the rubber blister did not occur, “B” representsthat abnormal hardness occurred, and “C”represents that abnormalhardness and the rubber blister occurred. *3: “HMP” represents highmelting point. *4: “N.M.” represents that the gloss value is notmeasurable.

In Table 2, the “surface state” is an observation result when thesurface of each of the fixing rollers is observed through an opticalmicroscope with 50-fold magnification. Further, the “gloss feeling” isevaluated relatively in four grades (A: Excellent, B: Good, C: Somewhatpoor, D: Poor) when the surface of each of the fixing rollers isobserved by eyes. The “Glossiness (image gloss value)” is a measuredgloss value by a handy gloss meter (“PG-1” (at 75 deg.), mfd. by NipponDenshoku Industries Co., Ltd.) when a solid image of secondary color ofblue is fixed on letter (LTR) paper. Further, the “rubber blister” issuch a phenomenon that the elastic layer silicone rubber is decomposedby high-temperature thermal deterioration during baking to cause localswelling (blister). The gloss values in Table 2 are also shown in FIGS.8( a) and 8(b). FIG. 8( a) shows a relationship between the primer layerthickness and the fixing gloss value in the case where the totalthickness of the primer layer and the parting layer is 15 μm. FIG. 8( b)shows a relationship between the primer layer thickness and the fixinggloss value in the case where the total thickness is 8 μm. As isunderstood from FIGS. 8( a) and 8(b), in both cases where the thicknessis 15 μm and 8 μm, a better gloss value is obtained when the primerlayer thickness is not more than 850 nm which is the upper limit of thevisible light wavelength (region) and the gloss value is furtherimproved when the primer layer thickness is not more than 360 nm whichis the lower limit of the visible light wavelength (region). On theother hand, when the primer layer thickness exceeds 1 μm, the glossvalue is not good relatively and is substantially constant even when theprimer layer thickness is further increased. This is attributable to aphenomenon that the cracks are liable to occur in the primer layer asshown in FIGS. 4( a) to 4(c) with an increasing primer layer thicknessto result in surface unevenness of the parting layer close in thicknessto the primer layer thickness. This means that when the unevenness isnot more than the visible light wavelength, diffused reflection ofvisible light due to the surface unevenness is suppressed and thus adegree of regular (specular) reflection is increased to improve thegloss value. For that reason, when the primer layer thickness is notmore than the lower limit of the visible light wavelength, aparticularly good gloss value is obtained. Further, when the results inthe case where the total thickness of the primer layer and the partinglayer 21 is 15 μm are compared with those in the case where the totalthickness is 8 μm, substantially same and good gloss values are obtainedin Embodiment 2 but the lower gloss values are obtained in ComparativeEmbodiments when the total thickness is small. From this result, it isunderstood that the present invention is particularly effective in thecase where the total thickness is small.

Further, with respect to the primer application (coating) method, whenthe wet coating and the dry coating are compared, it is understood thatthe wet coating provides a lower gloss value. Further, as in ComparativeEmbodiments 9 and 10, when the baking temperature is increased or thebaking temperature and the baking time are increased so that the surfaceunevenness of the parting layer is leveled, the gloss value is improvedbut the rubber of the elastic layer causes thermal deterioration(abnormal hardness or blister). For that reason, it is understood thatthe gloss value is not measurable.

As described above, according to the constitution in Embodiment 2, it isunderstood that good surface properties and prevention of the thermaldeterioration of the rubber which have been difficult to be realized bythe conventional fixing device are realized. Incidentally, therelationship between the primer layer thickness and the fixing glossvalue and the results of the thermal deterioration of the rubber in thisembodiment are also true for Embodiment 1 using the fixing film 2including the elastic layer.

In this embodiment, the fixing roller is used as the rotatable fixingmember but can also be applied to another roller so long as the rollerincludes the elastic layer and the parting layer formed on the elasticlayer. For example, the roller in Embodiment 2 can also be applied as itis to the pressing roller 6 of the fixing device. Further, the pressingroller may have a constitution including only the elastic layer of theroller in Embodiment 1 or a constitution in which the heat insulatinglayer and the heat accumulation layer are omitted and instead a solidrubber layer is employed. Further, the heating unit 13 of the fixingdevice in Embodiment 2 includes the film 15 but is not limited theretoso long as the heating unit 13 can apply heat to the fixing rollersurface and the elastic layer 20 as the heat accumulation layer.Specifically, a radiation heater or an electromagnetic IH (inductionheater).

While the invention has been described with reference to the structuresdisclosed herein, it is not confined to the details set forth and thisapplication is intended to cover such modifications or changes as maycome within the purpose of the improvements or the scope of thefollowing claims.

This application claims priority from Japanese Patent Application No.231312/2009 filed Oct. 5, 2009, which is hereby incorporated byreference.

1. A rotatable fixing member comprising: an elastic layer; a primerlayer provided on said elastic layer; and a parting layer provided onsaid primer layer, wherein said primer layer contains a crystallinefluorocarbon polymer having a functional group and has a thickness of850 nm or less, and wherein said parting layer is a coating layer of acrystalline fluorocarbon polymer.
 2. A member according to claim 1,wherein said primer layer has a thickness of 360 nm or less.
 3. A memberaccording to claim 1, wherein said primer layer and said parting layerhave a total thickness of 25 μm or less.
 4. A fixing device comprising:a rotatable fixing member including an elastic layer, a primer layerprovided on the elastic layer, and a parting layer provided on theprimer layer; and a back-up member for creating a fixing nip togetherwith said rotatable fixing member, wherein the primer layer contains acrystalline fluorocarbon polymer having a functional group and has athickness of 850 nm or less, and wherein the parting layer is a coatinglayer of a crystalline fluorocarbon polymer.
 5. A manufacturing methodof a rotatable fixing member including an elastic layer, a primer layerand a parting layer, said manufacturing method comprising: a first stepof applying a dispersion containing a crystalline fluorocarbon polymerhaving a functional group onto a surface of an elastic layer; a secondstep of forming a primer layer by drying the dispersion; a third step ofdecreasing a thickness of the primer layer to 850 nm or less by removinga part of the primer layer on a surface side of the parting layer; and afourth step of forming a parting layer by coating a crystallinefluorocarbon polymer onto the surface of the primer layer decreased inthickness and then by baking the coated crystalline fluorocarbonpolymer.